In the process of upgrading my bird's care but what would be the right course of action? What should I prioritize?

Hi this is me again with my bird Periwinkle for those who recognize the picture.

Little bit of backstory: I (20) live with my mom. My mom got Peri a month ago and thinks she's an expert bird owner because she's owned 10+ budgies throughout her childhood, but it didn't take me, someone who actually puts effort into research and care for her pets, long to realize my mom might have experience with birds, but she doesn't actually know sh*t about proper bird care. So I'm taking matters into my own hands :)

My plans in a nutshell: 1- get a bigger cage 2- get another bird 4- get more enrichment for in and outside the cage

I already bought a set of budgie toys off of amazon (2nd pic) and removed the bells. I put the one with the blue bell in his cage, I took this picture a few days before the toys arrived😅 Should I put more in the cage or should I make some DIY toys? (Links and tutorials are highly appreciated :))

And now my biggest question: Should I get a bigger cage or a second bird first? I'd get a bigger cage first, but money is a bit of an issue here.. I recently became disabled and don't have a job, so it'll take at least a month if not longer until I can afford a bigger cage, marketplace doesn't offer anything within my current budget. I can afford another bird right now, so if everyone here tells me to just stuff a second bird in this tiny cage I'll get a second bird as soon as I've trained Peri. My only issue with that plan is that I've heard people say you need 2 cages so you can introduce the birds in a safe way, and I do not have two cages, which means I'd have to get the bigger cage first, but then Peri could be lonely for an unknown amount of time...💀

So could anyone tell me what's the best course of action here? I'm quite handy so DIYing a cage is also an option if those are actually good for budgies (I'm a hamster and gerbil owner, especially gerbils chew through DIY enclosures in no time so I want to make sure budgies won't do the same thing)

Any other tips on improving Peri's situation right now are of course also welcome.