It depends if you want to walk around at your own pace without commentary or walk around with a group with a guide who is telling you things.

Only you can decide which you would prefer.

Getting a ticket would be easier if you get a guided tour because you don't have to understand anything except turn up at the start.

You can browse all the companies who offer guided tours here

https://granadainfo.com/alhambra_ticket_search.htm

or go and buy your own ticket at the official site  without guide here

https://tickets.alhambra-patronato.es/en


A good page with lots of info is here
https://granadainfo.com/alhambra/index.htm