Welcome to the game and the forum!
Here's one place to get started:
Elven Gems Marble Provinces
This link will drop you onto the marble province page. Notice that these pages are still labeled 'tournament'. The tournaments and map provinces used to be set up with the same enemy types. Tourney structure changed in early October
2021 2020 and these guides no longer apply there. But, they are still a very good introduction to combat basics for this game. Look at the rectangular bars on the left side of the screen, click on Tournaments, and you'll get a drop-down with a page for each of the province types.
Scroll down on the Marble page and you'll see a link under the 'Prepare' section that will take you to a page with links to videos for both human and elf cities. This should be available on each province type's page. Together, they will expose you to a variety of enemy matchups and help you get a feel for how your troop types will do against the various enemy troops.
There is a huge selection of videos on YouTube if you search 'elvenar combat'. If you're interested in Spire battles, most of those should have current information since the Spire battle structure hasn't changed much if at all since it came out. For tourney battles, if the video is pre-Oct 2020 the info is probably still relevant to that same type province on the map, but not specific for that type of tourney province any longer.
There's a Facebook group: Elvenar Platinum Leaf
They have loads of info on the game and my guess is they can point you to resources for learning manual combat if they don't provide it directly themselves. I don't do Facebook, so I don't have direct experience with their information there other than the public info they post for events and such and I've found that very helpful.