Hi & welcome to HC
I have zero experience of keeping any small rodent other than hsms so can't offer much advice or comparison between them, I know little about Chinchillas really, rats & gerbils are both social animals so you would need to do some research into group dynamics, introductions, possible problems with declanning etc.
Hamsters are solitary although some people do keep Robos or Russians in groups all species do best living alone as they are territorial animals.
Most people tend to have either Syrians or Russians as a first hamster as they do tend to be easier to tame & handle than either Robos or Chinese.
You may not be aware just how much space you need for a hamster, a cage between 80x50cm & 100x50 cm depending on species plus enough space for an out of cage play area.
Hamsters bond well with humans & some can be very cuddly too but not all, they are such individuals it's hard to generalise but they are great little characters, & most active in the evening & early mornings so you may want to think about how that fits in with the time you have to give them.
You'll find lots of info here on the forum that should help, maybe if you read some of the hamsters individual threads in the species section it will give you more idea of the kind of pet they are, if you have any questions just ask & someone will try to help.