It really depends on your personal preference and what you’re looking for. D2 may be slightly more competitive at the championship level, but is not really meaningfully more difficult to raise a team to the competitive level (ie, it’s not really harder to get your team to the ~B+ level at D2).
If your goal is to win championships as soon as possible with the team you choose, probably go with D3. If your goal is to move up to a top level D1 program quickly, choose D2. If you just want to learn the game, and have fun, then do what you want, it really doesn’t matter. You may want a mentor, or at least spend time looking through the forums though, because a lot has changed. Scouting can be fun, but an advanced version can be pretty complex (and you should know that at both levels you can land recruits in the D1 pool, and you should probably avoid scouting and recruiting the D3 pool ever, that should be considered just for sims). Once you land a team, don’t start spending scouting money until you know what you’re doing.