I know the current idea is to have real life money used to buy dungeon monsters and some special decoration tiles as the money earner for the game, however, I think it shouldn't be entirely the case.
This game's selling point is " design your own dungeon and quests for others to play them as well as explore players dungeons".
So heavily limiting the first option, will backfire in new player interests, therefor I suggest a little compromise here.
1) Dungeon master level based " creature or style" specialization.
I won't suggest free silver per level, that's way too common and boring way, how about instead at set dm levels ( and first one), player gets to choose either a creature type or a single creature as their " style or specialization", monster, that they can get for free, or a type of terrain.
You'd also get few monsters free based on your dm level due time, not too often though, perhaps every 4 or 5 dm level gives you one free pick for silver monsters or a floor style if you so choose ?
So, if you want to let's say make city related adventures,free player would spend their free design points to just get castle related dungeon tiles with these points, while a person who really loves wilderness related stuff, would use them to get bears .
With the level limitation being related to DM level , people have to make their adventures interesting, thus attract more players, and thus would be rewarded with more options for their dungeons, but in limited capability, this way if they want to be truly stellar they still need to pay money, but it won't limit them to the usual " just your party and humanoids with gold" setting with every dungeon and quest they make.
I belive it doesn't give them too much free things does it ?