Find a monofilament net that has at least 1.5 lbs/ft weight. I like 3/8" mesh, it will catch the 2.5" shad and up. 7' radius is the max you can use in Texas fresh water and that's what I prefer. Depending on which Academy you go to, they may or may not have the heavier nets. It seems like the stores near the coast do, that's where I get mine. My son has a 5' -1 lb/ft one he uses and now he catches most of our bait while I drive the boat, it just takes a few more throw as sometimes with a smaller net. I would shy away from the 3/4 lb/ft, I have used them and they take forever to sink. When winter time comes, you can tape it for deep water or get another net that is already taped.
For your livewell setup, keep some kosher salt and some foam off in your boat and your bait will thank you. A handful of salt and a capful of foam off helps the shad a lot. If your livewell is small, like most are, don't put many in there or they will expire quickly. I wish boats came with a 50 gallon bait tank built in, but I have yet to find one.