For test kit do NOT buy these test strips! They are soooo inaccurate, you may as well not even test your water then. Either get a liquid test kit from Tetra or API (I'm using API) these should contain: pH, KH, Ammonia, NO2, NO3. then you're all set. Yea they're lil more pricey then the strips, but for one they work, two they last FOREVERRR and a day and it totally is necessary to have on hand (sickness, tank cycling etc etc etc).
Hey that sound like a deal, just look at the silicon seals, make sure they're not missing/ busted and no cracks in the tank (pers I buy all mine used too and ALWAYS test fill them OUTSIDE first, let them sit some 24hrs and THEN they're allowed int he house lol).
Ask your LFS for ghost shrimp, they're the most common these days, also Petsmarts/ Petco's carry them. You just often would walk past them and not notice them...cause well they're ghost shrimps lol. Like my LFS actually orders me from their whole-seller whatever I want, they just don't have everything is stock
Angelfish, I'd keep in pairs in the 55g. They like it heavily planted; I'd prop mix plants like Amazon Swords, Vallis, Pennywort, Vallisneria, Cryptocoryne and maybe dawrf sagittaria for them. They do like floating plants, so either i'd use some of the pennywort as floating plants (works great, looks nice IMO) or buy them some frogbit plants.
Check your 55g thou when you buy it, you may need new bulbs for it; you can find these the cheapest at Lowes, Home Depot, Walmart by GE, Phillips Salvina, Bright effects. Often 55g come with hoods that hold 2x18" T5's...so there i'd get me something at the home store labeled as "Daylight or Ulitmate daylight" they're full spectrum (needed for plants) and check the small print , you'd want something in the range of 5-6500 Kelvin and then if its T5's I'd get something like 50-65 watts total over a 55g (that's how mine are set up). Reason I'm directing you to the home store...their bulbs cost you like $5 and the very same type light will cost you about $20 each at the fish store