hi, right now I’m a upper sophomore with a 3.55 gpa and what I really want to do in the future is apply for grad school at Columbia but I have no idea what steps I need to take or what requirements I should have other than a high gpa. What’s a good gpa for ivy leagure graduate school admission? What score would I need on the GRE? and most importantly how do you even fund graduation tuition?
Usually you go to grad school to study something particular or to get a credential that qualifies you for a specific job, not to hang a diploma on the wall that says Columbia. Honestly no one usually targets ‘Ivy’ for grad school, but rather the best grad depts regardless of the undergrad school. So what you need to do depends on the degree program. but a strong gpa is always good, especially in you upper div major coursework. Some programs will expect research experiences. GRE is tough because while no one really cares about it, a low one can weed you. It really depend on the program how serious you have to take it. Try to get a high score the first time.
Masters programs are usually but not always self pay.
Professional degrees are mostly self pay.
PhDs are usually funded by the universities with tuition waiver and stipend for TA or RA work.
These questions are all easily answerable if you take a few minutes to do a simple Google search. You need to do a lot more research on graduate school before you even begin to think about that, however.
Actually, a lot of these questions are not easily answerable by Googling. And even if they were, well, we exist to answer questions like this 
@BrownParent is right in that the program really matters - your answers will vary based on that. Plus, the rest of your record really matters, too. A lowish GRE score may be forgiven if you have a very high GPA and excellent experience. A low undergrad GPA could be forgiven if you’ve been out of school for 10+ years and have relevant experience or extenuating circumstances.
You should probably aim for at least around 150-160 on each section of the GRE - the higher the better, obviously. A good solid GPA for graduate admissions is a 3.5. At many master’s programs, you can get in with lower - and like I said, admissions are holistic and it really depends. (I had a 3.42, and I got my PhD from Columbia.)
And unless you want a PhD, expect to fund it yourself. Most graduate students fund their master’s degrees through federal loans. When you are on the graduate level, you can borrow more - up to $20,500 in federal Direct loans, and up to the full cost of attendance in Graduate PLUS loans (so let’s say you had to borrow $60,000; you’d borrow $20,500 in Direct loans and the remaining $39,500 in Graduate PLUS loans, which have a higher interest rate).