That question has many answers. For inexpensive, highly functional floats, I prefer the foam "dink" float. The Thill balsa floats are great, but most are designed for specific functions and you may need several types to fish all the water correctly.

Your best bet is to book a day with one of the many guides who fish floats or buy a good book. It is an easy and productive method, but like anything, if you fully understand it you will do much better.