It depends on the show your doing; I tend to use R18 for the warms and R65 for the cools, but you can go up or down to get the look you want, just don't forget that the intensity of your instraments can affect your look as well (I did that once and washed out all my other colour). Best of luck!
There are lots of great options for lighting. You really should let yourself free to experiment with combinations to get the one you really like for the show. However there are a lot of people just starting out who need a place to begin. So these are a couple of color combinations you just can't go wrong with. They are very high in transmission (very light in color) so consequently they have less overall lighting effect but that also makes them very safe for beginners.
For a little more dramatic feel: Warm: R2/R3 chose an amber, Neutral: R99 Chocolate, Cool: R60 No color blue
As I said, you won't win any awards for these combos but they are very safe starting points. As you develop your skills you will find you can use colors that are in the deeper pinks, oranges, ambers, yellows, and blues very effectively. The trick is that those deeper colors react more with set and costume pieces so they take some practice to develop those skills. If you can, set up a little light box with 3 lights that you can easily dropgel into to experiment with color, it's the best way to learn.
Spend some time reading the Rosco Gel page. They have a little description by each color of how it's different and what it's used for.