Ok well for starters, while it's bad that you built on your 1 side that had seats, that means you can do 3 straight builds without losing any seats. I'd see this as a better situation than I have, where I built up all 3 of the other sides on my first build, meaning that I didn't get to take advantage of the 3 free sides. So just make sure on your second build, you do all the building on one side, and then the third do all the building on the third side, and then the 4th building do all the building on the one remaining free side, if that made sense.

As far as player skills, make sure you've checked out guru's sticky at the top of this thread. I've used it (mostly) and it's served me pretty well thus far. If you're any good with Excel, consider setting up some kind of spread sheet that gives you a position by position rating for each player based on the skills that Guru lists. It's a great way to get you started, as initially positioning your players can be overwhelming.

On that note, also know that you're way better off putting players where their skills suggest, rather than their primary position(especially in your first season when you play a lot of bot teams, and the primary position doesn't matter as much). By the time you start to play a lot of decent competition in D.IV or higher, your players natural positions will have adjusted to fit their skills.