I agree with amity, modular cages just don't provide hamsters with what they need unfortunately. Hamsters don't naturally spend their time climbing and leaping about in the air, they spend time running, foraging, and digging. The problem with tier and modular cages is that the hamster cannot continuously run and forage and must slow down and stop or change motions to keep going through their enclosures. This is why these types of cages simply aren't recommended. Now I'm not sure what country you're in, but in the US, the IRIS bin cage is an extremely spacious and cheap cage to offer your ham, and it can be expanded according to your hams needs
If you don't live in the US, I'd go for the largest bin possible and add more if it's not as big as you'd like since bins are customizable. A 40 gallon breeder also works as an easy way to house your ham! Have fun buying and customizing a home for your little one!