I think the first thing should be figuring out where you want to use it and what type of conditions: fast moving river, out in sea; is it rocky, weedy?
Then, start with kayak type. Usually and most likely on-top for fishing purposes.
Then go get some basic recommendations for width and length of kayak based on where you want to use it and in what conditions.
Also do not forget to factor in weight and overall size when transporting kayak. People somehow often times miss the transportation aspect...
There are also finer aspects like materials: fiberglass is usual way to go, but if cheap then plastic ( https://outdoorempire.com/7-best-angling-kayaks-reviewed/
Then, basically go to any kayak shop online narrow selection down with your chosen features. See models and start Googling them and searching for reviews & opinions based on what you can afford.
Following these steps should get you a nice kayak!