For season tickets, I'd go at least half in with someone or even 3 people. 81 games is a lot of home games, and if you plan on going to only 5-10, its not really worth it. Sometimes its even tough to get rid of tickets (especially if the team does poorly).
If you were going to get a pair of season tickets, 500 levels are probably your best option. At least you can easily resell them at $10 or cheaper on Stubhub to weeknight games against crummy teams, and its easy to make a profit during a premium weekend game. Even if you end up eating some tickets, you wouldn't feel that bad since those seats are cheap to begin with. As well with season tickets (not sure if they do this anymore) you can trade in your tickets up to 25 times I believe for other games. So for example, if it was a weeknight game against the Rays and you wanted to get some extra tickets vs. the Yankees (in a similar area to your season tickets), they can do that during a trade in. Then it would be easier to resell those premium games instead.