Have a great time
In my limited experience of betting at the races I would advise
1) bet on the horse/jockey with the best colour scheme
2) Don't get totally trollied whilst betting (a mate from work did on a work jolly and thought he'd won the accumulator (?) He was jacking in his job and telling his boss what he thought of him, leaving his wife and I am told took some convincing that he hasn't won a bean! Just wish I could have seen that!)