You're going to love this game. If you take the time to read the manual from time to time, you'll pick up some new ideas each time you read it.

PB isn't perfect but it is lots of fun and I think it is a pretty good group of people you'll be competing against.

I think there are as many answers to your question as there are PB managers, but here are my thoughts.

1st - look through the rosters of various other teams to get an idea of the number of pitchers they keep.

My goal is to have about 19 pitchers and 16 position players at the start of the season. That is not because you need that many pitchers, but because pitchers are more difficult to predict and I like to have a few "prospects" on the roster who may not pitch many innings.

The number of pitchers isn't as critical to the game as the number of innings they pitched. If you have pitchers who pitch fewer innings, you need more pitchers.
In RT, you never know when a pitcher may be injured or benched, so I think you need a little more pitching than in TRAD - at least at the start of the season. In addition, the more pitchers you have, the better chance that a few of them will actully perform well.

If you have solid front line pitchers who you expect to get an MLB start every 5th game, you don't need as many pitchers as if you have rookies or marginal pitchers who perhaps have their starts skipped or move back and forth from starting to the bullpen.

Some other suggestions:

1) Don't make a lot of trades right off. Learn some of the quirks of PB and also how your team plays. The other managers are nice guys, but they are competitive and you aren't likely to get the better end of trades and could get ripped off. It's tempting to make a lot of trades right off the bat - but don't. Be patient. Chances are the guy who had your team before you had a reason for putting some of the guys on your roster with whom you may not be familiar.

2) Take advantage of the monthly FA drafts in RT. That is a great place to build your team. If you have a strong team, you can use the draft to pick up rent-a-player types who may not have many PA's or IP's but nice stats or nice defense. If you have a weak team you'll get high picks. Last year for instance the top picks in the 5 FA drafts in my league were:
Chad Tracy
Zack Greinke
Kevin Youkilis
David Wright
BJ Upton

Pretty nice pickups. Don't miss out on the monthly FA drafts.

3) Avoid trades where you give up 1 guy and get several. In order to get in the monthly FA draft you have to cut your roster to below 35 (one pick for each player below 35...up to 5 total). If you trade 1 for 3, you'll have to cut 3 guys just to have a chance to be in the monthly FA draft.

Lots more thoughts but I'm too long winded already and you probably never got this far. Sorry. I get carried away I guess. I do enjoy the game and hope you do also.

Dave

Orcutt 99RT5
Bement 98RT1
Salusan K15
Malaga D5