If you have any questions about API usage, addon development, LUA, addons and so forth, definitely join the ESOU Discord and ask Wheels about it all! You are also free to join the ESOUI Addon Developers community on Glitter.
Below you can find some links that contain great information on how to get started with addon development, as well as information about the API itself.
While some prior coding experience is helpful it's definitely not needed to develop addons. Addon development is actually a really good way to get into coding if you're looking to learn!
Here you can find the majority of the basic information about the ESO API, as well as some great tutorials to get started in creating your own addons. I would highly recommend reading through some of the pages here if you are interesting in creating addons, there's some very useful info.
One major complaint about the ESO API is that it is very poorly documented, which will become apparent on the wiki as very few functions have much info associated with them.
This is the raw source code of the ESO API, which while less friendly to look at when first starting, is probably the most effective way to figure out how a given event or function is used in context. Most of the key information about how the API works can be found here, and the rest is (unfortunately) passed around by word of mouth by other developers (that's what this channel is for!)
Lastly, here are a few developer tools that are incredibly useful for creating addons of all types:
Mer Torchbug - Fantastic inspector tool, probably the one I use the most.
Zgoo - Similar to Torchbug, another useful inspector.
TextureIt - Helpful tool for examining various ingame textures for use in addons.
Black Book Browser - Not an addon per se, but this is a much more powerful extractor/examiner tool for game files.
ESO Profiler - Profiling tool to inspect runtimes and performance of addons and components of addons.
DebugLogViewer - This goes with LibDebugLogger, if you use the lib in your addons or have addons with it, this tool lets you view the logs and filter them so you can get much more useful info.
For everything else, you can check ESOUI's Developer Addons (this category is not shown in the Minion client)