Hi mate, i haven't read the previous comments apart from Pianomans one which is spot on! but what i was going to say is it also depends on what distances you want to shoot to, if you want to shoot more than 50 yards (Which as a person new to it all i doubt you will) i would go for a .177 as its more forgiving when using holdover and under. Whereas if you just want to shoot between 10-40 yards then a .22 is best in my opinion because there's more knock down power and as your not shooting far the holdover isn't that bad if the gun is sighted as 25 yards. I use a .22, even for shots further than