Watch rogers sporting goods, they have good deals on trap loads. Stay away from winchester super target and universal, they undercut you on shot big time. My favorites for both 20 and 12 are as follows.
Remington STS and Nitro 27
Winchester AA sport
Remington Gun Club
Remington game load 8’s (not legal in some trap shoots)
The rem gun clubs and game loads are very economical and are what I usually shoot because of costs. I also reload but unless you throw out $300 and reload in bulk it isnt any cheaper than hitting sales. Be sure to watch [censored] sporting goods, they run the gun clubs and game loads for $4.95 a box all the time.