Must-have: Build Up and Ring of Fire.
Consider: Fire Sword, Fire Sword Circle, Consume.
Maaaaybe: Blazing Aura (tiny radius), Combustion (long animation, DoT), Hot Feet.
Avoid: Burn (tiny radius, scatter, longish animation, DoT, can't be used while flying)
Don't worry about taking little from /Fire. You can reasonably skip the entire secondary except BU and do quite well, doubly so with the primaries that are strong enough to stand on their own (Archery and Fire).
Ring of Fire does high damage, and is usable as a ranged blast. Fire Sword/Fire Sword Circle are strong high-damage blaps. Consume refills your end and lets you abuse Blizzard more. The slow from Hot Feet and Ice Storm will stack to help reduce scatter, and Hot Feet is a huge (20ft radius) damage aura. I only have experience with Ice Blast on a Corruptor, but if I were to make a Ice/Fire Blaster I'd probably play it blapper-style: go in with Hot Feet running, Ice Storm, FSC, blap and blast the remainder to death coupled with Blizzard + eat small blue + Consume everytime it's up. IO wise, I'd think of going for a high S/L defense build with Frozen Armor from the Ice APP.
Fire manipulation on paper sounds like a decent way to supplement a primary which is largely single target. Unfortunately, that's only on paper. In reality, you'll take way too much damage before you get a chance to unleash some of those AoEs. Combustion and burn in particular will root you and will cause you to die before you finish animating the power. This isn't to say they aren't decent if you're teaming alot, but you'll rue them if you're soloing.
Fire sword circle is a nice power. Fast and does good damage. Blazing aura isn't that great largely because you have to be right in their faces for it do damage. Not so great for a blaster primary like ice which has long range blasts. I'm not a fan of hot feet, largely because it draws a lot of aggro for minimal damage (yes, I'm aware, it can do a lot of damage over time, but we're talking blasters without mitigation, not fire controllers).
I'd suggest you reroll if your blaster isn't high level yet and if you're not particularly tied to concept. There are better synergies with other combinations.
Fire/Ice - opposite of what you have but better. Fire is high damage, and have both good single target and AoE options. Ice manipulation, as opposed to having just more damage, actually has some nice mitigation utilities such as a hold, an AoE -recharge and slow and ice patch. It's a pretty solid combination.
Rad/Fire - works better than Ice/Fire because you have a PBAoE damage powers in the primary that work with powers like fire sword circle. Point blank damage powers work pretty well if you can deliver them quickly and defeat your foes before you take much damage.
If you're dead set on playing this combination, the advice that Laevateinn gave is solid.
My first 50 was an Ice/Fire and I did find myself skipping alot in Fire Manipulation. I took Ring of Fire, Fire Sword, Build Up, FSC, and Consume. I had Combustion at one point but never used it so i got rid of it. I found it to be fun, a bit difficult, but fun.
I'm a Mac user, no Mid's for me
Thanks for the replies! I think I have kind of become disinterested in Blasters though. It has nothing to do with this thread, I just love the Corruptor AT too much. I swear, I'm having the hardest time figuring out a hero AT that actually holds my interest. 
Right now I've been working on a lowbie Ice/Fire Blaster. My choice of Fire as a secondary was to supplement Ice's weaker AoE. I was planning on skipping Fire Sword, Burn, Blazing Aura and Hot Feet. Since my power picks are so sparse in my secondary I am kind of thinking I'm approaching Blasters or Ice/Fire wrong.
I guess I'll start here: what powers would you consider "must-haves" for /Fire?
I also wouldn't mind hearing some opinions on any good Ice/ or /Ice combos that don't sacrifice too much for a decent IO build. Some power combos just seem to mesh nicely when it comes to IOs.