Buckhorn is right about the quality of shells....and if I were shooting a big tournament, I shoot nothing other than factory new, Remington STS.../ and I will still shoot their 1oz load of 8's at around 1185 fps...( for Trap singles from the 16 yd line ...or even out to the 20 yd line)...
....but my assumption, since you're purchasing a pump gun ..is Trap is a new game to you ...and you're learning / and probably shooting Trap singles from the 16 yard line..( where all of us started ---- and I shot a pump gun for a long time at Trap and Skeet for that matter )...so the reality is, any shell will work just fine. Especially when you're learning - you don't need premium shells.
In my opinion....16 yd singles....can be shot with 9's or 8's ....even 7/8 oz of shot is plenty...1 oz is also fine - but you don't need that much shot ...and you sure do not need 1 1/8 oz shells...for 16 yd singles. ( when you earn your way back to or behind the 20 - 27 yd line, shells start making a difference in tournaments )
....and for 16 yd singles, I shoot a Modified choke
Work on your fundamentals....stance, gun mount, focus on target, make sure you follow thru on every shot..( pulling the trigger is the start of the shot - not the end of the shot )....and learn.../ keep a small pocket notebook on how you're doing...if or where you miss, which station..../ and self evaluate after every 4 rounds or 100 targets.../ don't just throw lead downrange...practice smart ( and shooting 4 good rounds of practice is better than 8 rds of just blasting away ).....and all of that is 99.9% of what makes up your scores !! ).... not which shells you pick...in my view...