Ok, got an idea on a kayak...now what safety/electronics?

[AFARR]

I'm leaning towards an OK Trident 13. Small enough to be relatively handy for fishing local streams/lakes, but big enough to go out in some salt water (and if I get better to go out further).

Now...I have NO experience in fishing saltwater from a Kayak (and I've only been on a charter boat a couple of times).

What safety gear is mandatory and what is necessary (as they aren't quite the same).

Also..a fish finder. I don't want to haul a car/boat battery around at least yet...so if I'm going to experiment with one, I think an inexpensive battery (AA/9V) powered finder would be best for me..since I have no experience with them.

GPS? Need one or not? (I'm planning on fishing around the OBX the end of Sept...including kayak fishing, possibly charter and definitely pier and/or surf. I don't intend to go out of sight of land...however....someone pointed out that in the sound, you may get lost in some of the back waters. I have GPS on my phone...but I think it's tied to a map rather than being able to locate via topo / ocean maps.

Looking for inexpensive stuff to try out at first.

Thanks!