Here is a proposal of material, it is what I currently run on both of my tanks (price indication in Germay in 2022.Q4):
Required:
Return pump Aqua Medic DC Runner 5.3 -> 160€ (quite variable)
Air pump Eheim Air1000 (silent pond aerator) -> 100€
Moving bed bacteria support Evolution Aqua K1 micro -> 1L 10€
Optional:
Heater Aqua Medic Titanium 200W -> 40€
Thermostat Inkbird WLAN ITC-306A -> 40€
UV sterilizer Evolution Aqua EvoUV 25W (pond version slightly better than aquarium one) -> 120€
Cartridge filter triple Aquafilter 10" three-stage in-line system + 3 x empty transparent (better) cartbridge -> 40€ (quite variable) + 20€
Mecanical filtration
Rollermat Filter paper 20cm x 100m -> 20€
Chimical purification
Silicate (as well as phosphate, barium, arsenic, chromium) remover Arka Microbe-Lift Sili-Out 2 -> 1L 25€
Zeolite Arka Microbe-Lift Zeopure 5-9 mm -> 1L 10€
Optional: nitrogenous organic waste remover Seachem Purigen -> 0.5L 45€
Optional: aragonite AquaLight Calcium Carbonate CaCO3 4-6mm -> 10kG 22€