Arguably the hardest blaster combination to play. Fire/Fire has almost no mitigation except the afraid in Rain of Fire and the slow in Hotfeet. Compared to other blaster variants, you will tend to die alot.
With that said, you're also arguably the highest damage blaster combination as well. Aim, build up, fire breath and fireball will melt just about anything. If they survive that (doubtful, but possible) you can follow up with fire sword circle.
Stuff to take:
Flares - animation is so much faster than days gone by. Also one of two powers you can fire off when mezzed.
Fire blast - good solid blast. Also the second power you can fire off when mezzed.
Fire ball - good ranged AoE, no reason not to take it.
Blaze - a short range, but very high damaging attack. It's your best single target attack.
Inferno - a high powered nuke. Since you're all about damage anyway, there are times when you want to take a huge spawn with you.
Fire sword circle - a very good AoE, but it's point blank. Use when mobs are either mezzed, taunted or close to death anyway.
Aim / Build Up - *DO NOT* skip these. They add to your damage. And in some ways, killing stuff first before they kill you is your best mitigation.
Consume - a power that will allow you to recover end after you nuke or you run low. The biggest draw back is that it's a PBAoE and it causes aggro. It's a great power...for a tanker, but as a blaster, it's a bit on the sketchy side. I recommend you taking it but with reservations.
Optional stuff to take:
Blazing bolt - it's good as snipes go, but honestly, you can kill stuff faster using other powers.
Rain of fire - it's one of your very few mitigation tools; however, it has the tendency to scatter mobs which may irritate teammates. It's a good power to use when mobs are taunted/held/immobilized. Damage for this power is often underestimated.
Fire sword - a moderate damage single target melee attack. Not bad, but not that great. Honestly, there won't be that many times you will use this if you have your other powers well slotted.
Combustion - it's another PBAoE but with a slightly longer cast time than fire sword circle. While it can do more damage than fire sword circle, most of the damage comes in ticks which means stuff will shoot back at you while they're being cooked. Fire sword circle's damage is mostly front loaded. I've seen a lot of fire blasters die trying to use this.
Stuff to pretty much avoid:
Blazing aura - it's a great power...for a tanker, but if you're mostly at range, you won't get much mileage of this power. Some can argue it's a decent power if you have teammates holding/immobilizing mobs. I'd argue that most of those mobs will be dead from your other AoEs. The only thing it will do is eat endurance.
Burn - another power that on paper sounds decent. However, the power has a number of problems. First it has a similar afraid component as rain of fire, second it roots you to a spot as you summon the burn patch and third, it just doesn't do enough damage to justify the power slot. The power is questionable for fire tankers unless they have some way to keep mobs in the patch. For a fire/fire blaster, it's very skippable.
Hot feet - it's a great power...for a controller. My fire controller loves this because it provides containment, does good damage and works well with fire cages. For a blaster, it's an aggro magnet, an endurance hog and does less damage than the other powers you have at your disposal. I'm sure you're thinking you can use hot feet to slow mobs to give you time to fire off your PBAoEs (combustion and fire sword circle). After dying a lot, many blasters come to realize the flaw in that strategy. You just take too much incoming fire to make the power usable. Paired with another primary, it may be okay. Paired with fire blast, the power is skippable.
Blasters are designed to be flexible. They have powers which in conjunction with powers from team mates such as buffs or IOs can play the roles of other ATs should it be needed. Hell I know one who plays Tank. It'll never be as good as one but it can do.
What are you going to be about? Single Target Damage? AoE Damage? Are you herding and nuking? Is it conceptual? The Phoenix concept is the most doable one. Some people maybe in teams and it just so happens that the -10 fly in hotfeet rounds off the teams capabilities.
I don't think powers suck, they just have a time and a place, you need to select the ones you see a use in and prioritize out of them what you see yourself getting the most of. As I level up I add to what I feel I could do with.
All in all, what's skippable could be only for you to know unless your interested in making something that's no different from most any other Fire/Fire out there.
He will honor his words; he will definitely carry out his actions. What he promises he will fulfill. He does not care about his bodily self, putting his life and death aside to come forward for another's troubled besiegement. He does not boast about his ability, or shamelessly extol his own virtues. - Sima Qian.
Fury Flechette is spot on with his post.
It's generally accepted on the forums that it's pretty hard to gimp yourself when building a toon, but the fire secondary is the exception. It's actually pretty easy to gimp yourself with /fire.
"All in all, what's skippable could be only for you to know unless your interested in making something that's no different from most any other Fire/Fire out there."
The reason you see many similiar Fire/Fire build are because the /fire secondary has some very poor choices. An 8ft radius damage aura. A droppable aoe pet that won't deliver much damage unless you first immoblize the target because it causes run fear. A high endurance medium damage pbaoe that causes run fear/scatter. A high endcost, medium radius pbaoe that has a 3 second root and takes 8 seconds to deliver its damage.
I have an alternate build that uses rain of fire, slotted up burn(combined with either char or ring of fire), and hot feet, and it does reasonably well.
My primary build doesn't have those powers, and it does astonishingly well.
Don't take combustion early, take it late when you just don't have anything else to take. It's a waste of endurance most of the time, unless you're up against high conning mobs and the dot will actually apply.
The medicine pool will help you a great deal, as you can slot aid self with 2 interrupt reductions and fire it off between dot ticks.
I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them.
Thomas Jefferson
I think Fire/ and /Fire are optimal when combined with other sets, personally. Fire/Fire is overspecialized in dishing out damage, if that's possible to be. Your mileage may differ.
If youre just starting him, i'd try to reroll as fire/ice. Ice has the mitigation that they speak of in shiver and ice patch. Ice patch, then RoF is nice. Have fun either way. 
And in regards to pairing Fire with other sets, Fire/Mental's probably the PvE powerhouse of Blasters. Adds even more AoE and some single-target, psionic too, and Drain Psyche slotted for regen is going to keep you in good shape, and wiith maxed endurance. It doesn't need slotting for recovery: one hit, unslotted, gives 75% +Recovery. For comparison, unslotted Stamina's around +25%, slotted Stamina around +50%. Also adds a great debuff component against hard targets, as Drain Psyche's also -Regen for 30 seconds.
World of Confusion also seems to serve well (though I admit I haven't used it without a set of 6 Confuse purples in it for some time). When jumping into a mob it frequently has a pseudo-placate effect on all minions, with the nice exception that it doesn't shift attention to your allies. Gets frequent use, too, as Drain Psyche is worth jumping into a mob to fire.
Added bonus: if facing Rikti, and you go to stand by a Guardian that's not fired AM yet while blasting stuff, can often confuse them just as they fire AM and steal it. Stealth IO and Stealth from Concealment help in this, as World of Confusion doesn't aggro or break stealth.
And a small note in regards to ancilliary, the god-mode from Force Mastery, Force of Nature, only has -100% recovery when it crashes unlike Surge of Power. With Drain Psyche up you'll not notice the -recovery and, frequently, won't even toggle-drop from the crash as your endurance was maxed and it's only -100 end, even if you have 105 or more max endurance from accolades/Safeguard temp powers.
Anyhow, forgive me if that was perhaps too much information.
In regards to Fire/Fire, I'd share the opinion in that it overspecialises. I think Flechette was pretty spot-on, so afraid I've not much more to add on that front, other than to once again emphasise the glory of Build Up and Aim. When your main mitigation's sheer damage, those two powers are what'll make it work.
And to perhaps to say: "Why on Earth would anyone pick Blazing Bolt when it's in the same powerset as Blaze?". 
I have recently created a toon of a fire/fire blaster. LOVE IT! The damage is nice and to me, it appears not much End. drain. But I started out on a full team in the sewers.
Any advice? I am a team player alost all the time. What powers can I skip? I have had this problem on taking powers that suck.
She-Fire on Freedom