Hi pal
Best pellets are round heads - air arms, jsb, fx & daystate are all made be the same company jsb and comr in 2 different head sizes 5.51/5.52.
Set a target at 25m and zero your scope to this range, practice hitting a 1" size circle ( 2p coin ) and then practice at all ranges up to 50m in 5m increments so you get to know your holdover/under.
Hope this helps
Atb
Scott