UG's identity crisis is embodied well by its gold cards - it went from the consensus worst guild to this in a year:
to say nothing of Shardless Agent, Edric, Mystic Snake, and so on. Many of these cards drag you in different directions - a curse, because it makes it hard to set up a clear signpost if that's your goal, and a blessing because it opens up more design space. Plus, all of the UG cards above from the last year+ are strong enough that they go in almost any deck. Some directions:
Flash
Green has been a secondary flash colour for a long time (to the extent that WG 'Faeries' has been a good deck in my Cubes for years) and we've seen many more explicit flash incentives in green recently (Nightpack Ambusher as the most mainstream one, . This can take on an aggro-control or outright control nature. Card dump:
+1/+1 Counters
Simic has been slated since the OG Ravnica for its exclusive focus on +1/+1 counters (joke's on them now I guess!). Green still does most of the work here but blue adds some unique twists (Deepglow Skate!). Sample deck:
Combo-Control
If you want a more combo-control feel, there's something like this:
Or if you want a tricky creature deck (the perfect Opposition deck if you're that extreme!):