You'll get as many opinions as there are fish. read them all and try to figure out what will work best for you. Here's mine:
Tank - Hold out for a 75g, you and the fish will be happier.
Filters - I only buy AC110's for HOBs. I put one on a 75g 2 nights ago that only has shrimp and crayfish and a sponge filter for a 10g. The tank was in bad shape, within an hour it looked good, in 24hr's it was spotless. IMO, AC's are also easier to clean and you don't have to buy replacements cartridges. I've been unimpressed with the Marineland 400's I've had. I have an ac110 (ac500) that's over 15yrs old and still running like a champ on the orginal motor and impellar (in fact that was the one I moved to the 75g).
Cycling - Since you have friends with tanks, have them clean a filter in a bucket and take that gook and water and dump it into your new tank. In less than a day your filter will clean out your tank and be cycled or close to it. I've never lost a fish doing a fast cycle with dirty filter water. All that gook is loaded with BB. The tank will look like crap for a day, but it's a good thing.
Substrate - Someone mentioned sand instead of gravel, I'm right there with them. I put small power heads near the bottom of my tanks which blow all the poo into the water column for the filter to pick up, I rarely have to vac my tanks, most never get it; on new tanks, sometimes the powerhead will blow eerything into a pile, I keep repositioning the powerhead until the flow in the tank keeps that from happening. Pool filter sand is great, natrual look, heavy grain so it doesn't sucked up in the filter (avoid play sand) and it's cheap.
Ligthing - I'm in love with metal halides. I'd have them on every tank if I could. But it's unlikely you'll buy those for your first tank. Next up I'd go for T5 10k gives a clean bright light.
Fish - since you will only have one fish, consider ordering from one of the MFK vendors. I've used Rapps and Fishfarm several times with good results. The quaility of fish will likely far surpass that of a petsmart fish. Look at their lists and you'll find fish that most LFS don't carry. You could end up with something you like more than a GT or JD; just research the fish you are interested in to make sure you can accommodate them long term. Also, find out if there are any fish clubs in your area, local breeders are another great source for nice fish.
Good luck and keep it up you're on the right track.