The masteries you run depend on which champions you're wanting to play, so that would require a bit of research. I suggest reading through and understanding what each does, then looking for specific mastery pages for champions you like to play (you'll notice some slight differences with overarching patterns). A standard is 21-9 for offensive, 9-21 for defensive.
A standard AD rune page is:
- 9x Flat AD reds
- 3x Flat AD quints
For AP, it's:
- 9x Flat AP or Magic Pen reds
- 3x Flat AP quints
Both will usually have:
- 9x Flat armor yellows
- 9x Flat MR blues
Anything beyond these rune pages are specific to a champion or role, but these two as your first two will cover pretty much every champion as a standard.