Cynette, Jelly Drover Deck Tech
Just Keep Bouncing
If there's one card I'm known for, it's my beloved Unsummon. It's in my gamer tag. It's in more of my decks than any single card, including Sol Ring. Some value dual lands or Power 9; my prized possessions are a handful of Alpha Unsummons.
So, when I found out that there was a new commander in Foundations that wants to be bounced and is a clear homage to honorary Irish Jellyfish Man-o'-War, I was entirely on board. And, as a Games Club and Anime Club chairperson, I welcomed wholeheartedly our new Unsummon-loving waifu with anime art.
Core Synergy
Cynette, Jelly Drover is a solid win condition, if it is a bit slow and grindy. When she enters, she makes a 1/1 Jellyfish with flying then gives creatures with flying +1/+1 and flying, effectively making her tokens 2/2s. As anyone who has played a mono-blue or Azorius deck with a commander with an ETB effect can attest, however, we don't want to use it fairly. No, we want to double it with Panharmonicon!
We also want to use blink effects to control the ETBs and use them over and over. Irenicus's Vile Duplication is a particularly powerful effect, as it ignores the legendary rule, so we can use it to copy our commander and stack the boosts, too.
Dour Port-Mage is a single-card engine in a deck like this: it bounces our commander and draws cards while we go through our paces. Deadeye Navigator's time in the spotlight might have been as ephemeral as his ability, but this is just the kind of deck to bring it back... and forth and back and forth.
Of course I have to include both my favorite card and the inspiration for the commander, Unsummon and Man-o'-War, respectively. While blinking is a bit more efficient, bouncing is a solid way to protect threats, such as in response to a board wipe, as well as to be able to turn the engine card into a removal spell in a pinch.
After all, Unsummon can target an opposing creature, while Siren's Ruse can't.
Win Conditions
So...we're bouncing things back and forth, netting a 1/1 or 2/2 flyer each time; when opponents are Sneak Attacking big nasties, like Blightsteel Colossus, how do we keep up? We go wide with those tokens, as seen in the Core Synergy, while also beefing up our Jellyfish into a veritable army of evasive beaters.
In addition to Unsummon effects as tempo advantage, we have one-sided board wipes, which are always strong ways to create the openings needed to smash opposing faces in. Since our Jellyfish army is made of tokens, we can freely bounce all nontoken creatures, leaving them intact. And if we happen to bounce Cynette? We just replay her, which we want to do anyways!
Draw
Since our Jellyfish tokens share a creature type, they're perfect for Pol Jamaar, Illusionist, who draws cards equal to the amount of creatures we control of a type. We can even bounce or blink Pol for massive card draw if we're having trouble ending the game.
Since our Jellyfish have flying somehow (I mean they float, but are we really going to skip over how weird this is?), they are excellent at getting in chip damage as evasive beaters. Even before our pump spells and mass bounce comes in, we can use that evasive chip damage to draw cards with Coastal Piracy effects, filling our hand every turn.
Perilous Research and Skullclamp are solid ways to use our excess little dinky guys for fun and profit. Remember: without Cynette on the board, the Jellyfish are 1/1s. That's when they can be freely popped with the Clamps. Just don't make the mistake of trying to Clamp them with her out, or they'll survive!
If we want to use those bodies while they're still around, Meeting of Minds and Artistic Refusal are strong convoke spells that we can cast with the excess bodies. Refusal, in particular, can surprise people as a "free" counter, either protecting our board or denying the opponent a game-winning spell!
Ramp
Ramp may seem a bit out of place in a low-to-the-ground evasive beatdown deck, but we do need to cast multiple spells in a turn...or, to be more forthright, the same spell multiple times, with or without some number of spells in between. As a result, we have some cost-reducers, most notably Kefnet's Monument, which is another fantastic tempo generator.
The Banners, both Heraldic and Patchwork, help with some of our mana problems while also providing incidental mass pump to our little blue Jellyfish. They really pull their weight, as we need anthems to threaten relevant damage and we need mana to keep our engines going and to power out some of our more expensive spells.
The general plan is to get our commander out, bounce and/or blink it a bunch of times, and beat down with an army of small, evasive creatures. We can make our creatures bigger or destabilize our opponents' boards if the initial plan isn't working, and we can draw lots of cards in the process.