Begginer help!!!

Hi people! I'm starting to think in playing ultra marines. They are quite flexible so in my first 40k matches seem like the best choice.

We are playing our first matches at 500 points.

Can i get some advice?? What should I bring to the fight? I might be buying the combat patrol (rule of cool, i researched and I know is not the best choice) but i'm not limited to those models

I don't know what i'm facing, but should I bring something anti-vehicle, terminators, etc??

Any advice on list building and strategic? How to move on tablet? Good combinations? I'm looking to have fun and learn more than winning, but victories are always welcome.

Thx in advance!!