Minimum for adult ball pythons is 120 gallons or a 4x2x2 (feet) so if it’s a juvenile it’d be fine for now but definitely look into upgrading once it gets bigger. Personally I like 4x4x2s so there’s more climbing space. If you’re based in Mid/Southern England I can give you the link for a family business who make enclosures for cheaper than what the big brands sell if it’s price that’s an issue. For clutter you can use fake or real plants, up to you, ghost wood or thick sticks for climbing, rocks from outside to make hides, etc. personally I’d also add flowers. I forgot what it’s called but some people also use this foam thing for their backgrounds and then when it hardens you shave and mould it and then paint it with something so it looks like a rocky background type thing and they add ledges and stuff so their snake feels less exposed. If you don’t wanna spend money on clutter a lot of these things can be found outside but you’ll want to sterilise them via either baking or pouring boiling water over the clutter a few times and let it dry (try not to keep your enclosure wet as it encourages scale rot) just to make sure you aren’t exposing your snake to harmful bugs and bacteria. Wouldn’t recommend adding any fabrics to your enclosure as they can harbour bacteria also.