I [20M] want to propose to my girlfriend [19F] but I'm scared of messing it up

I wanna start by saying she mentions atleast twice a week that she wants to get even just engaged we can be engaged however long we need she just wants me to be her fiance

But I'm scared that she will still say no if I dint get a big enough ring because i dint make all that much money to be fair so it may not even have jem

So what do you guys think?