First thing to determine since you know the size of the tank, is the filtration. I agree with Bryon and a canister filter like a Fluval 405 would work. There are a few other brands, but start with Fluvals and go from there ... IMO.
Are you looking to do a fishless cycle or a fish-in cycle? Sounds like your looking to cycle your tank with fish so you will need hardy fish ... I used TigerBarbs .... They are hardy, colorful, energetic and a bit aggressive so you'd need to keep them in a shoal of at least 6. Plus they are hardy enough to withstand a range of pH and temperature levels. However, there are other fish you could choose from, I'm sure someone else can give suggestions.
Yes you will need to invest in a good test kit and the API test master's the way to go. Don't worry too much about trying to test for hardness, it'll be what your water change source water is ... most likely your tap. Check with your water company. I'd also look into Seachem Prime as your de-chlorinator / conditioner.