We usually use "Go for it!" to encourage someone to take action. For example, I'd ask my friends if I should do something, my friends think it's a good thing to do. They'd tell me to "go for it". They often would add "Good luck!" at the end as well.
During games, we'd say "defense" when our team is in defensing position.
If I was not doing too well, my friends would say "good job, better luck next time." Or "nice try", but it's not really "加油吆！"
The closest translation may be "Good luck!"