I'm by no means an expert, but here's what I know:
There is a trade off between net size and castability. I have two nets -- a 6 footer and an 8 footer. It doesn't sound like a big difference, but the 8 foot net covers 70% more area than the smaller one. On the other hand, it was incredibly frustrating to learn to throw the larger net, and it is a lot heavier. So I'd say for a first one don't waste your time with a tiny net, and don't go bigger than 8 ft. Mesh size determines the size of the bait you catch. Mine are 1/2 mesh -- too big for small minnows but good for shad. The tradeoff there is smaller mesh size = a slower sinking net. The third tradeoff is weight. More weight = faster sinking but also is tiring to throw. I would watch a lot of YouTube videos about technique, then get a cheaper midsized net (around 7 feet) and practice a lot in the back yard.
