I find my 11 speed shimano 105 needs adjusting once or twice a year to keep everything piss perfect. That's all the maintenance it needs other than changing tires and tubes.

If you only have one bike to work on, then doing other things like replace bottom brackets, changing cables and housings and even changing chains are going to be many years down the road. So I wouldn't stock pile tools until you need them. You might find the tools you use to remove something won't be the tools to put a new model on with.

You said you got a new bike I think.... did you take it back for that free tune up they may have mentioned? Around here that would be a decent check and adjustment of the shifters/derailleurs. Also a check of the brake and wheels with spoke tensioning and truing if needed. Sure you can do that yourself, but if the bikes new and still in warranty, now isn't the time to be completely DIY.