Welcome to the forums, homeschooler!
As for your question, I had the same issue with my Sapphire a few years back (hence why I ended up selling it). However, I ended up getting Ruby after a while and I'm trying out new Pokemon that I didn't use before, such as Roselia and Walrein.
My suggestion is look at some types that you are always going to want on your team, like you'll probably always want a good water type for Surfing and such, and pick one you haven't used before. Use Pokemon that aren't really considered that good, like Volbeat or something, as it will give you a challenge. Maybe you'll want to make a team of all one type, or make a team of Pokemon that aren't fully evolved.
Another suggestion is to check out the Nuzlocke challenge, you can find out about it here
Again, welcome to the fourms, have a good time here.