I've downloaded some games from this website, but when I use a dex drive to put them in my memorycard, just the scenario takes up 80% of the space, an then the system also takes up a lot plus all the custom characters an stuff. How are you supposed to fit all the game in a memory card?
Thanks!

You're supposed to use multiple memory cards for this.

About 3 memory cards will allow you to play most games made with RM.

Thanks, I have 3 memory cards, so I think I can play most of them.

Games that use more than 3 cards, you could probably still use just 3, as the extra cards are likely extra scenario cards. Get through the first scenario, and when it asks you to go into the next card, get rid of the old data and put in the new scenario data. The games you need to watch out for are games that require you to switch back and forth between cards for whatever reasons. Mine is one of those, but it's only on 3 cards total, so it shouldn't be a problem so long as you have 3 cards (which you do).