I have the base model iPad Pro. It’s the best purchase I’ve ever made from Apple. Ultra powerful (double the 2017 Macbook Pro lol) and runs IF like a charm. Never had any issues and always run maxed out settings with no lag. However, it also costs around $800 so not really a budget purchase. If it is in your budget then definitely go for it - you won’t regret it.
Edit: I didn’t see your price limit - personally, I would wait until you can affort the best product possible (the iPad Pro) and buy that. Only buy it if you can justify the purchase though - I can because I do all of my revision for school on it using GoodNote and the Apple Pencil which is brilliant along with many other apps. I can’t help thinking that you’ll have buyers regret if you get something cheaper. Despite the fact that all iPads are great and premium devices, the iPad Pro is built for speed and that is what you need. If you cant justify the Pro, get the Air. From what I hear it is an excellent device.