As far as lane splitting, start with best advice ever for a new rider: don't.
Seriously. Get a good six months riding under your belt first, at least. Take the basic riders course (BRC) and work on developing skills.
As a fellow So Cal rider that does split lanes, you need to develop the basic skills first. You need to see and anticipate dangerous situations well in advance, and that's for general riding. Lane splitting is a whole new ballgame.
Once you have the basics down and at least six months experience, stock up on clean underwear.
I agree...just develop basic skills and worry about that sort of thing later. Learn how to see the road well, starting, shifting, cornering, stopping, and staying alive are the most important skills.
As far as avoiding collisions in the dirt, are you serious? I have ridden in the dirt for 30 years and never had an issue. Dirt riders are very courteous here, and it isn't like they won't see you. If you are going too slow they might give you a honk and you just pull over and let them by. Never just blow by someone without communicating, you're likely to scare the dickens out of them and that's when people crash and get hurt. If someone is very slow on the trail they are likely either new or older, in either case you want to pass them with understanding.
Basics first, you are already starting to count your chickens before they hatch. Lane splitting can be very dangerous if you don't have knowledge about the basic operations and safety of a motorcycle.
I don't have much experience on dirt, but what I do know is that knolls in the trails can be dangerous if there is no set traffic pattern. Ask my husband. He was coming up over a knoll on his ATV, not knowing his brother was coming up on the otherside with his dirt bike. They collided and the back tire of the dirt bike hit my husband in the head. He died three times on the way to the hospital, spent time in a coma, spent three months at Gaylord learning to walk and talk again.
Take the BRC and learn to ride. That's pretty much it. I don't agree with lane splitting but that's just my opinion.
When I say learn to ride I mean really ride, not just go in a straight line. Practice skills, practice awareness.