Welcome Ian.
My advice to you is to get your own life straightened out.
If you can succeed at that, then you stand a good chance at getting your GF back and your best friend.
I think you need to own up to your financial shortcomings and get all of that figured out - That will show your GF that you are becoming a responsible trustworthy adult. Anything else in my opinion is just window dressing and not likely to solve your financial problems and not a long term solution in terms of keeping your girl friend.
DO NOT WORRY about getting her back right now - first of all - its not your main problem even if you think it is. second - i fear you will use money (i.e. buying more gifts) in an attempt to woo her back. so DON'T EVEN THINK about it.

There are many financial counselors that specialize in helping young people with poor finance skills. I am not one of them, so you need to find one. But I can think of some obvious issues -
1. Are you working, and are you working enough? (Sometimes you have to work more than 1 job to make ends meet, especially if you have debt already to pay off.)
2. Why are you living somewhere where you can't pay the rent. You should find somewhere cheap to live - even stay with your parents until you can get rid of your debt - and offer to help your parents around the house - cook, clean, and even consider paying them back later or a small amount of rent to show you are serious about this.
3. Stop trying to find "too good to believe" financial deals. Everything costs money and there are always fees and interest rates to contend with.
4. Stop using your credit cards!! Seriously!! Personally, I live on my credit cards - but I pay the balance in full every month. Until you can comfortably pay off your credit cards EVERY MONTH without late charges, interest, etc - I would STAY AWAY from them. Use a debit card - that will keep you in your budget.
5. Learn to live on a tight budget - Ramen noodles cost about 99 cents for a pack of 5. I lived on those for a long time and they are not bad! Stop eating out. Look for good deals. Learn to live within your means.
6. Stop trying to impress your girlfriend with money! Does she think you are somebody you are not?? If she has thought all along that you are some rich dude with money to spare - then you are right - she may not come back to you - because you aren't that guy. If she loved you for you and not your money however, then maybe she will come back - once you can at least support yourself - not to mention support her and a whole family one day in the future. No woman wants to marry a guy who can't be trusted to balance a check book - that is why I suggest you get you and your finances straightened out before you even bother to court her. She won't be interested until you've gotten all these bad habits straightened out. Most women don't need to be won over with money anyways - it sounds like your GF valued trust over money anyways - so I'd go for the trust route in the future with her.

Anyways - that's my advice off the top of my head - but you need PROFESSIONAL help with your finances. You will be facing some hard times - but there is no quick fix - don't look for the easy way out - just get to work and do it.