I would personally advise against two things:
1). Don't go for a corporation with big numbers just because they have big numbers. You'll be sorely disappointed because there's only a few options of mass-scale RP corporations. Depending on your RP style, you may or may not find an agreeable group. For that matter, not every - hell, not any - large RP group I know has ALL RPers, so you might still end up with a small percentage of RP friends despite being in a 1000 man setting.
2). Don't expect larger corps to take in a novice character. The reason I joined AI was that although I was only at about 2mil SP, the corp gave me a chance to learn and have some freedom. I learned more in the first months of my time with the corp than I could have asked for, and I've grown close to the other pilots.
Larger corporations aren't looking for friends, they're looking for assets. Unless you have the 5mil, 10mil or 15mil classic barriers, you're not going to have anything to offer them, and they don't want or need you. Call it a lack of perception of how useful an eager noob can be, but it's the way of the world.