That's a lot of GTA dollars to play with!
Wanna share some?
I've ranked to level 66 but have spent all my money buying and modifying cars (same as real life!).

Rank up to level 50 and phone merryweather to send in their peacekeepers to air strike random places. Costs $12500 a time.

Phone Lester and set $9000 bountys on random players. Costs $10000 a time.

Have you got all the boats and aircraft for sale on the in-game websites?

Are you in a crew? Crew car colours,crew logos on the car bonnets and crew coloured tyre smoke all cost $25000 a time.

Depending on rank level you can buy military vehicles like the Buzzard attack chopper (my personal favourite) or tanks. These cost a couple of million.

Or you can set up a second online character. They will share the same money as your first but you start from rank level 1.

Even if you did all of these I think you would have a large amount of cash left.

Best advice I can give is to throw $50,000000 my way.