What do I need to know about Ethereum before throwing some euros at it every month?

Is it good for long term hold? Thinking about throwing something like 50€-100€ every month.

English is not my first language and I do not understand what gas fees are. I've googled it and still don't understand, but what I did understand (i think) is that it is not worth putting like 100€ to do something with it because the gas fees would be too much or even more than 100€? If someone could explain gas fees to me in a very very simple english, I'd appreciate.

I just wanna buy crypto every month, withdrawal it to my cold walltet and hold.