It depends on what type of fishing you do.
1. Just going from the ramp to a spot to bait fish in a small electric only lake.
A 30 lbs transom mount with a group 24 battery.
2. Bass fishing and/or moving around a lot in a small electric only lake.
A 30 to 55 lbs transom and/or bow mounted with a group 29 battery.
3. Bass fishing, moving around, traveling long distance, trolling for long periods, fishing in a windy area. A 45 to 55 lbs bow mounted with either a foot controller or something like an ipilot with 2 group 29 or bigger batteries.
Trying to troll and fish with a transom mounted trolling motor can be a handful, especially when its windy. It requires constant steering. A bow mounted motor will pull you around instead of pushing and requires less attention. A foot control will free up your hands and allows more time fishing or tinkering with stuff.
A Minn Kota with ipilot is the Cadillac of trolling motors. It allows you to walk around the boat and fish without having to constantly steer. But some people prefer a foot controller over a remote control.