Best way to learn

[notluck]

I have been playing(if you can call it that) golf for 7 years. However, I stink, I can't even finish an easy 18 hole course, this may be due to the fact that i never had a lesson. I am willing over the course of this summer to spend 300 on golf. What would be the best way for me to able to get me to finish an 18 hole course and even better still get under 100?

Thank you,