It seems like it is pretty hard to screw up a earth/fire build. But IMO from the primary set the only skippable powers would be salt crystals and perhaps the single target immobilize.
From fire i think i have just about it all. Power pools are the normal, fitness line, hasten, and then your travel powers.
I would say to start with on the control side, work on getting the ST hold, Stalagmites, and Volcanic Gases fully slotted ASAP. Quick Sand and Eearth Quake are both great powers but thankfully dont require alot of slotting in early levels to be commonly useful, so those 2 can wait until you get a few more levels under your belt, though you might get a second slot on earthquake for recharge, QS is pretty fast to come back up.
The fire assualt set should be looked at as any other damage dealing set, get a couple accuracies on each power and then work on damage hancers. Get some recharge going ASAP on firey embrace, especially with domination its a great thing to have up as much as possible.
As for money, if this is your first toon or first villian i can see money being tight. But if not, then if you have any other toons with cash on hand i say transfer some over. Personally i usally use SOs until level 32. Though you might have to buy a couple sets, IMO i would rather do that and then at 32 i can get level 35 IOs which are basicly now as good as SO++s and will never expire until i choose to replace them.
If your in a bigger SG you might also talk to some of your members. Some people farm making the IOs for badges, if they are making them anyway might kick them down to you for nothing to be a favor for a group member. Now though i might not normally suggest this for the purposes of leveling, you might also look to take a tour through a MA farm team. Even if not for just leveling, you will probably earn a handful of tickets in 1-2 runs which can then be used to make some recipe rolls, then go sell those recipes and get some start up cash that way.
so my dom is lv 22 now and im in need of a build good for both teaming and solo. but im still very new to building toons so if anyone has a build idea id appreciate it. also is it bad to still use training enhancers? i wanna do IOs( or w/e they are called :S) but they are too expensive for me.