I think building a set of barriers for $15 is a great investment. Being smooth in your dismount/remount can gain you a good number of places over people that struggle.

Pre-riding the course at least twice will give you an idea of how fast you can take corners and how you want to attack certain hill sections (run vs bike). I find it's good to have a feel for the course instead of riding blind.

I think some 1 minute intervals are good from a dead stop to simulate the start of the race. Being in the first couple of lines helps before the course gets tight and things slow down. Suffer early and then find your rhythm.