I've had my boat for 2 1/2 years now, and the single best investment I made was a quality GPS with quality aerial imagery. Specifically, I got the Standard Mapping Texas-One GPS base map for my Simrad GPS, and it has been crucial as I've navigated the reef-laden bays in the Rockport area.
Basically, instead of a map base layer, it is a high quality aerial image that was taken when skies and water were both clear. You can see reefs, channels, and much more. I have been able to avoid high-speed encounters with reefs and have been able to navigate potentially treacherous areas with confidence. I know without the map, these would have been a much more anxious couple of years with more time in the shop and less time fishing.
In addition to the safety component, it has also helped me identify structure (shell vs. grass, dropoffs, etc). My favorite fishing spots today are places I found because of the imagery. Of course, I've tried tons of spots that looked "fishy" but didn't hold fish. But a few of the spots have pretty reliably held fish, and it's really fun having spots you've found that even local guides don't fish.
I discovered Standard Mapping because the Lowrance/Simrad rep at the Houston Fishing Show said I should go talk to them. I wound up buying my unit from them as well, and the package is cheaper than buying them separately. Also, I just got the "Classic" level, and it has been plenty. The upgraded versions have more information for offshore, but the Classic has had everything I've wanted and needed.
Here is the link for Standard Mapping:
https://www.standardmap.com/product-page/texas-one-classic