You want to go cheap, right?
We can't undo the purchase of crushed coral or a biowheel, but we can work with what we have.
You're going fish only, most of the folks on this board are reefoholics and are convinced you'll be one too. There are some shortcuts you can get away with.
a) If you can't afford better filtration, don't buy any expensive invertabrates (shellfish.) Some snails and hermit crabs will make tank cleaning easier, but beyond that and you're going to need to invest heavily in live rock and the protien skimmer.
b) Buying a single chunk of live rock will help kick-start your biological cycle. The more good quality live rock you add, the faster your tank will cycle. Faster cycle, means you can get fish sooner.
c) You can get away with less filtration if you understock the tank. Standard stocking rule for saltwater is 1 inch of fish per 5 gallons of water. I suggest you start with one small fish, test your water quality regularly, and add an additional fish when ammonia = 0, nitrites = 0 and nitrates are under control. As someone else mentioned, saltwater fish can be expensive, so it's best to go very slowly.
d) You may want to go for a skimmer when you can afford it. Probably before you get your second fish. A protien skimmer actually removes waste from the aquarium instead of breaking it down into other organics. This is most important when you have some sort of tank disaster, your biofilter can not increase it's filtering capacity in a hurry; the protien skimmer however, can be adjusted to work faster but less efficiently in an emergency situation.
e) I'd go with just the powerhead instead of the extra filter. Over time you can add one piece of live rock at a time until you have a pleasing aquascape and lots of biofiltration area. Your crushed coral also supplies some biofiltration area, although aragonite sand would have been better. (The sand will make a bigger dust cloud than crushed coral, but after it settles it has more surface area for biofiltration, and is softer to the gills/scales of fish that like to dig.)
f) If you're sticking with crushed coral, don't forget to regularly clean it with a gravel vac or similar.