^This! A drink or two will calm the nerves, any more will mess with your reaction times and you need to be on top of things, save the partying for AFTER the set.
Get the best gear you can afford, new tuning machines are $100 if you cant afford a better guitar. EVERY string player should have a tuner and tune between each song while the singer speaks to the crowd.
The expereince should motivate your band to correct its issues, not every gig is going to be perfect and growing pains are part of the process.
Money? Do you play for money?