Wheels are very individual. What works for one person might not work for another. Your skating style and comfort level will help you determine what wheels to use.
The floor we skate on at LSF is sport court. We also frequently skate on polished concrete and outdoors (during the warmer months). Our skaters mostly skate on mid-80's to low 90's durometer (hardness). Wheels are normally sold in sets of 4 (enough for one skate).
A lot of skaters skate on 2 different brands & hardness. Just make sure you get the same diameter for both sets. (59mm or 62mm are best for beginners and derby)