I would learn the basic camera first. Get familiar with the controls and your shooting style. Figure out what you like to take photos of. You don't really know that yet, even though you might think you do. The worst that can happen is that you are proven right
Figure out HOW to get the shots you want. Then as your skills increase, add lenses and/or strobes. If you can't take photos with the basics, you aren't, imho, really going to get the most out of any add-ons.
With wide angle you will need the strobe or you will only be able to shoot natural light as the lens blocks the internal flash.
Wide angle is great as you can get nice and close for a wide reef scene/wrecks or larger creatures. You can also do CFWA - close focus wide angle shots. In these you have a strong element that you are very close to (often almost touching the lens/port) that you light with your strobe and then also the scenic in the background (lit or not). Very interesting type of photo. But hard to get right.
Close in underwater photography is essential as you have less water to steal your light, soften your photos and give you backscatter.
I personally prefer shooting macro stuff so I added my Inon 165 macro lenses before the WA. And I shoot more macro than WA by a huge margin. I just like poking around in holes to see what's there
Many others prefer the WA by a wide margin. Different strokes as they say.
It's essential that you figure out what suits YOU. We can give you our thoughts, but we can't decide for you (no matter that we feel you should simply do as we tell you! LOL). There is no wrong or right in this adventure - so have fun!
FWIW in order that I would buy stuff:
1 - camera
2 - housing
3 - external strobe
4 - macro lenses (two to stack!)
5 - WA lens
6 - second strobe
