The A major scale is a good major scale to get familiar with early on. It is one of the more common keys for songs and musical pieces, especially when guitars are involved.
The key of A major has three sharps in it. The notes of the A major scale are A, B, C♯, D, E, F♯ and G♯. All the open strings except the G string are part of the key. This makes it nice for bass guitar, the more so because the root is one of the strings (and a low one at that).
The F♯ minor scale has all the same notes (it is one of the modes of A major), making it the relative minor of A major. If a song's key signature has three sharps, chances are it is in A major or F♯ minor.
This article goes through how to play an A major scale in different hand positions on the fretboard. You may find it helpful to read about bass scales and hand positions first, if you haven't already.