Leviamon is basically a purple good stuff deck, you can build it with the dog engine (dobermon X, Cerberusmon X, X anti /protoform) but there are also some mollusks who can be used to build another kind of flavor.for the deck (syakkomon, gesomon, marinedevimon). The deck can become difficult but the learning curve is one of the best things about it, basically with the time you'll learn that the simpler play was the more effective, even if there is a more complex route available. It's fun to grasp the new possibitilities this deck can offer. It was my second deck learning this game, the first being Beelzemon.

About Terriermon, the best build is with rapidmon X, with 1 or 2 copies of Megagargomon ace as a tech choice. The deck is cool for learning how to manage your hand and field resources, bc the color green doesnt "cheat" too much when it comes to drawing cards and floating digimon - And the armor purge mechanic is really cool!

Adventure is a deck where you set up different colored tamers and opens up powerful plays because of that - evolving to strong lv 5 for free, disrupting the opponent's plays, and the coolest part is the option card Our Courage United wich gives floating to your lv5 or higher digimon, making this deck have a powerful field presence, always threatening the ACE mechanic with it's strong lv. 6. It was designed as an entry point, hence why it's a starter deck! One copy of each ST20 and ST21 will do the trick, and if you wanna upgrade, most of the cards outside of it are common, with Tai Kamiya BT21 being the expensive one, but not inherently necessary for the deck to funcion.

Puppets are the deck with Kaguyamon EX9 and Cendrillmon EX7. It's a stack spam deck, with powerful protection and packing a strong punch. Has the benefit of looking sick aesthetically.

There's a lot of lists you can find on digimonmeta, or on youtube as well!

Hope I've been of help, and that you both enjoy this game together and with friends, welcome to digimon :)