I'm not sure Charlotte doesn't need the Gucci money. Charlotte is obviously much richer than you and me. But it doesn't mean she is that wealthy.
Yes, the Grimaldi are wealthy. But the money of Monaco is the money of Monaco. Maybe Rainier left her something from his private money when he died, maybe he didnt't but in any case, she is just one of the many nephews of a ruling prince.
And, yes, Stefano was a succesful businessman. But when he died, his money went to Caroline, not the kids. How much of this money has Caroline passed on to her children. Probably some of it. But most probably she is still administering most of what Stefano left her.
Also, there is a common mistake. When someone is worth a lot of money it doesn't mean that he has all that money disposable to spend. When you read this people fortune is x millions, it doesn't mean that this person has so much cash. The money may be invested in several companies, buildings, etc... and you need to invest and re-invests your winnings.
What I mean is we really don't know how much money Charlotte really can spend on horses. And international horse-riding is awfully expensive. It's not just that you have to buy the horses. You have to pay their food , the trainer, the groom, the shows, the travelling, the vets... Just taking a couple of horses and a groom to Brazil is unthinkable for most people! She probably wouldn't be able to own 7 horses and travel so much with them if it weren't for the Gucci sponsorhip. Or maybe she could but the expense would be so much that it would force her to lower her way of life and she doesn't want to.
I don't find anything wrong in Charlotte attenting party after party, either. I [-][/-]don't get why she should do something boring and serious with her life when she has the means to simply enjoy it, and I don't get why she should focus on one thing, or work hard on anything, or find a purpose or whatever. Most people don't do it. Not even normal people who need to work to pay the rent. Why should she? Sometimes it sounds a little bit like envy.
And I know I have been very critical with Charlotte! But not because of her lack of purpose or her many parties. Only because she is fake and she tries to sell herself as something she is not and she is under no obligation to be.