Should I try host a game as GM if I just joined?

As title said, only joined a few days ago. Would I ruin someone's day to try do this? Or should I just play more as a character for starters?

You're not going to ruin anyone's day by trying to host a game that they'll enjoy.

That being said, Gming is hard work! If you've Gmed other systems in the past you'll be fine, but if you're brand new to TRPGs in general you might want to play as a character for a while until you've got a better idea of the basic rules :)

A user said to me before (sorry I forgot who you are), to try and host about 2-3 players on your first few sessions as a GM, then work up to 4-6 players as you gain more experience in Gming. Unless you have previous experience in Gming with a big group, I'd say play as characters for a bit, then move on to Gming.