I feel for you. I did the same thing - spent about £40 on a 3 tier Rotostak thing which even had a 'dining room'. Within 3 weeks we had to upgrade our hamster to a cage which met RSPCA minimum standards. I kidded myself the Rotostak was ok at first because we liked it. But our hamster seemed a bit depressed and lethargic and also got quite aggressive and chewed at the one little section of bars to try and get out. It wasn't till he grew large and got stuck in one of the vertical tubes that I googled to find out more about good hamster cages and found most of the answers were on this forum. We immediately bought an 80cm by 50cm Savic cage (after reading that the RSPCA minimum recommended continuous floorspace for one unit was about that), but I actually wish we had got 100cm x 50cm cage at that time as 80 x 50 really is a minimum and fills up quite quickly once you have a Syrian sized wheel and a hide in it. I've recently upgraded ours to the 100cm Barney cage, which is great and costs less than £50 and find it just the right size for a large Syrian hamster. Our hamster really loves having more space to do hamstery things in and never tries to escape.
The biggest problem with the rotostaks is - you can't fit enough bedding/substrate in - they need a minimum of 3 to 4" of substrate and ideally more than that. If you have 8" or more bedding they can start digging their own tunnels and burrows which makes them happy and they can do their own thing a bit in their habitat. Ours has about 6" in his cage and a large house/nesting box which is big enough for the big nest he has built, is nice and dark inside (they like sleeping in the dark) and also fits his potty litter tray inside.
It did take our hamster about 10 days to adjust to his new bigger cage and he was a bit nervy at first, but by day 10 he was climbing bars and having a whale of a time. He had lots of places to hide and sit, could rearrange his substrate as he liked it and could run in a larger wheel with a straight back and he just looked happy.
The other big problem with the rotostaks is they can only fit a very small wheel. Syrian hamsters need an 11" or 12" wheel really. They need to run so their back is in a straight line or they can get back pain or spinal problems. Nearly all hamster cages, including Rotostaks, only come with a very small 6" wheel, which is only big enough for dwarf hamsters.
Once ours was in the bigger cage I realised how totally unsuitable the rotostak was. And it hurt a lot spending more money, but in the end I just binned the whole thing. If you have one of the larger base units it could be good for storing things, or you could use a couple of the larger tubes as cage floor toys (if they are big enough). But generally Syrian hamsters need rat sized toys.
If you have a look on zooplus they sell very reasonable cages that are a suitable size for a Syrian hamster. Basically this is their 'habitat' where they can bury hoards, run around and have space, and a house in the cage is their hide where they can build a big cosy nest. What I really didn't like about the Rotostaks, more than anything, was when I realised the hamster had no option but to go down the tubes, to get from one unit to the other, whether he liked it or not.
Some of the cages on zooplus are too small as well, but the Barney, Alexander and Alaska are good ones and there are some more expensive tank style and perspex cages as well.
Hamster Cages | great selection at zooplus
Some people have returned cages that were too small and got a refund. If you've only just got it, I would try doing that, even if it's been used. Sadly manufacturers just want to sell cages and some are totally not fit for purpose.
I now cringe to think of our hamster virtually sealed into a large tupperware box with a few tiny holes in. Like Piebald, we had one for a hamster many years ago as well, when they first came out and before knowledge on Hamster care had moved on. Ours had free run of the room though and the unit was left open all the time, so that probably helped back then.