Well it's a good question considering that we don't know what you like in board games, number of players you can get around the table, your prefered theme, max number of hours of play, etc…
But, having the game and some expansions, i'll try to guide you a bit with what I know about Runebound.
-1ST: DungeonQuest: Which I own, is completely different than Runebound. The only similarity is it's based of the FFG world of Terrinoth and some characters in DQ are compatible in Runebound (at least my french version of DQ gave me the 6 character cards to use with Runebound). DungeonQuest is a game of silly randomness and dungeon exploration. It's card driven and luck plays a huge part in this game. For me and my gaming group, it fills a spot when we feel like just having lots of fun and laughing at each other misfortunes. The goal of the game is to exit the dungeon, alive, and with the most treasures. In our numerous plays, more often then not we die a horrible and hilarious death on our in or out of the dungeon. It's random, silly, fun and quick to play. 1-4 players, around 1.5 hours.
-2ND: Runebound 2nd edition: Which is one of my favorite game I own. It's an adventure game set, again, in the world of Terrinoth. You play 1 character that venture de map and try to accomplish challenges, level up and be the first to either kill the big boos of gather 3 Dragon Runes from numerous Dragon Lords. It have a kind of "race" mechanic where you compete against another player to be the coolest champion around. the game is quite simple on it's surface and doesn't need many plays to graps it's mechanic. In the base game, each turn the active player have 5 phases to do: Refresh (return activated cards), Movement (roll movement dice), Market (if in a city), Adventure (if on an Adventure token), Experience (pay X Adventure tokens to level up and take 1 XP Token to bosst a stat).
One of the coolest mechanic in this game is the Movement dice. You have 5 big dice with terrain types on each of it's sides. When you roll them for your movement, you must choose one symbole on each die and move your character around the map. It's pretty neat and even though it's a little luck-based, it still leaves you with some control on where your character will go.
But, you must be ready for long games at first and for that, many will tell you, and they are right, that it's best played with 2 players, 3 tops! My normal 2-player games take 3 to 4 hours. It's a little bit slow at first since your almost a zero, but when you start harder challenges it's getting rewarding quickly. The principal reason why it's slow it's because there's almost no interaction between players, unless they do some PvP which I tell you it's pretty rare. So, during the other player turn you watch him do it's 5 phases. A turn may take from 1 to 3-4 minutes depneding on the card you draw. One thing though if you're a little imaginative and willing to do it is reading the flavor text on the cards so the non-active player can get in the ambiance and see what the other player's adventure is.
It's really is a solitaire adventure game played with others hheheh. Each character is writing it's own story, one turn at a time.
If you like: Long games that reward you later on, some downtime when not your turn, seeing whats happening to the other player and follow it's own adventure, don't mind readin falvor text to help other players get the feel on your story, immerse yourself in an epic adventure in Terinoth?
Than go get this game!
-Concerning expansions: My favorite, for the base game, are the Items&Allies and the Challenges types. Items&Allies will simply add more cards in the market deck of the base game. you simply shuffle the expansion cards with the base game cards and voilà.
Same thing with the Challenges expansions. You simply add them to the Adventure decks of the base game for more variety in the challenges, encounters and events.
My favorite Items&Allies expansions and the ones I would recommend for the base game: Weapons of Legend, Rituals and Runes
My favorite Items&Allies expansions and the ones I would recommend for the base game: Traps and Terrors, The Dark Forest, Terrors from the Tomb, Drake and Dragonspawns, Beasts and Bandits.
The other types of small expansions and the Class deck and the Adventure variant expansions. I won't talk about the Class deck since I don't own any of them and heard they're not really necessary. The adventure variant can be cool if you feel the base game starting to get boring and you'd want to refresh it a bit. What it does is simply replace the end game goal with a new one. The instructions will tell you which base game cards to replace with the expansion ones.
-Concerning Big Box expansions: Those are cool! They add a new board overlay, new characters, new mechanics. They keep the Runebound feel to them but let you roam new lands and accomplish new goals. I bought 2 of them and probably won't buy any more.
My favorite Big Box expansions: The Frozen Wastes and Sands of Al-Kalim. FW let you play in a frozen wasteland in search of the lost Princess. You have some new cool mechanics for discovering long lost aftifacts and eventually, the Princess. OR, you can simply level up enough and go kill the dude in it's northern settlement before any player bring him his Princess or kill him first.
Sands of Al-Kalim I didn't tried yet but I can already tell it's gonna be huge fun. I love desert settings and this one is pretty cool. It has a sandstorm that moves around the board and alter some places on the board.
Another one that people seem to like is Mist of Zanaga. It's in a swamp area with awakening gods…don't really know the setting but it looks pretty neat too.
Well, that's all I can think for now. Hope I could help you a bit in your decision and don't hesitate to ask anything!