Keep in mind that every piece of equipment you add increases the complexity, the task loading and of course the price of your system.
Price wise things are quite obvious hence I will not mention money again - you know what you can afford. Here is a list of other things you have to consider:
Auto/TTL sounds easy, but adding a strobe (let alone 2) is not that simple. Strobes have volume hence occupy space, they have weight so they affect your system's trim and buoyancy, they attach to arms (extra things to be careful with and control during the dive), they need fiber cords to fire (with which you also need to be careful during the dive). The list goes on. eg you need to adjust the location and orientation of your strobe(s) from shot to shot (not always but very frequently).
Also with experience (and extra equipment like strobes etc) what you consider as minimum acceptable quality of your pictures increases. For example without strobes let's say everything more or less goes. Add a strobe and now you want good lighting (ie nice colors, even lighting, no burnouts etc). Now add a second strobe and you also want/expect no shadows, good balance between the two, even more uniform lighting etc. It is not easy to manage all these.
Another thing: the more options/things you add the easier it becomes to destroy a shot especially for a beginner. This is because usually the range of accepted settings or choices for a nice shot is quite limited compared to the range of all available settings and choices. The beginner tends to leave things to chance (be it by choice or by ignorance) at best, or simply quite often make poor decisions, hence chances are that wrong settings will be used destroying the shot.
The list goes on and on. U/W photography is not easy.
The question is, do you really know why you need one (or two) strobes, or you want to add one (or two) because everybody else does so??? If you know why you need strobes for the kind of photography you do and roughly how to use them you should also know if you need one or two. If you don't know why you need strobes then I suggest you do baby steps. Start with one, see what benefit you get at what cost (I am not talking - only - monetary cost here but mainly the cost of how complicated things become u/w), get used to the task loading etc and of course you can always add a second (or third) strobe(s) whenever you think you need one and you are ready.
Going from no strobes to 2 strobes is a huge step that I think you'd better avoid for now.
Good luck