Newbie training tips

I dont think you need much upper body strength - but lots of cardio fitness. And practice your mounting /dismounting technique too.

I wouldn't bother with running training at this stage. You'll get the odd race (maybe 1 in 20) where running fitness makes a huge difference; otherwise, it's not as important as you might think.

Dismounts and remounts are useful, and you're going to need to get them cracked at some point, but that might not be the easiest way to make up time; you're generally only doing one or two per lap, so even if you lose 2 seconds on every dismount and another 2 on every remount that's well under a minute for a typical race.

I'd work on cornering and off-camber riding. In particular, learn to get round the technical sections with an absolute minimum of slowing down; that's where the really big gains are to be made. Find/make yourself a training loop that replicates some of the more technical parts of a race course, and ride round it, trying to use the brakes as little as possible. Then work on going faster, while using the brakes less. The less you slow down, the less you have to speed up again, and the less energy you use.

If you can find a coached evening training session in your area, that'll be hugely beneficial; lots of clubs run them, often welcoming members of other clubs, though it may be a bit early in the season at the moment.

Some good suggestions already. Two things I'd add.

1) Lot of the speed over a lap comes from figuring out where you carry speed, where you conserve and where you go all out. Observe riders faster than you, and learn from what they do. Think about your pacing during sighting laps, have a plan in your head about where you'll attack if you need to break up a group. If there's a technical section that doesn't suit you, think about how you'll minimize the damage that's going to do to your speed. You can neutralise a single track by getting to the front, you can often be faster running than riding, think outside the box. Learn from others during the race, think on your feet.

2) When I look at a cross race power file, there is hardly any time ridden at threshold. It's all way above or way below. So train accordingly. The guy who can sprint the hardest the most often wins. I do one session of sprint or tabata intervals per week in the early season, and two in the late season.