Just a couple of low-cost ideas:
If the elevated lunge tracks focus on a single leg at a time you can do them off of a yoga block as well. It's cheaper than buying a stepper.
But as a beginner you will be fine without the elevation.
If the weights are a bit light for squats you could purchase a set of bands like this to add resistance (these cloth ones are awesome compared to the rubbery ones) :
Walito Resistance Bands for Legs... https://www.amazon.com/dp/B07H7QT6BN?ref=ppx_pop_mob_ap_share THESE! I had what sounds like the exact same rubbery type bands as you and the exact same problem. They rolled up and drove me nuts. I wish I had just gotten these in the first place. Note: they smelled real funky when they came. Like aquarium fish food. I left them out on my porch for a couple days and now they’re fine.