Your schedule or what line you can potentially hold is based on your relative seniority. It is very likely to be on RSV for a few months as a new hire.

As an example lets say you are a new F/O with a seniority on the F/O list being 550/600. That means you have 549 F/O's ahead of you. If there are only 500 regular lines, you don't have the ability to hold one, unless someone senior to you bids RSV (it happens). In your case 49 people senior to you would have to bid RSV before you get a line.

Always bid what you want and not what you think you might get. You never know why people bid the way they do and you can be surprised at times. At the same time be careful how you master bid because you may get something you put in for (different airplane, base etc) unexpectedly.