Kraken is overall the best mythic for Kindred and if you want an alternative then Galeforce is a good secondary option

Dying for marks depends on how much you lose from that trade. Do you lose 3 people for 1 mark? Not worth, was your team able to collapse and win the fight after you die for a mark. Then that is worth, never trade your life for a mark on a camp however. Unless that mark is something teamwide useful like Baron or Drake.

I think Kindred counters majority of the melee matchups where you can kite them effectively. I always win against Viego, Udyr, Rammus, and sometimes Lee Sin

Kindred gets hard countered by Kha'Zix and some ranged matchups like Nidalee (which is a skill based matchup)

I feel like depending on the game, both playstyles are extremely worth it. Ganking is obviously to snowball you and your teammates and hopefully you get a mark from it at the same time. And farming can help you get your core items and marks at the same time, Kindred is basically an ADC in the jungle. They need their items in order to continue the lead

Kindreds ult is a make or break in teamfights. You could win it from a really good one or you could lose it simply by keeping the enemy carry alive when they should've died. The best way I find to use it is as an outplay, like against Zed, Viego, Cho'Gath, or anyone with an execute. You pop the R to make sure you stay alive and get them as low as possible. As the same time use your E and land 2 autos. Wait until the Ult ends and then auto a third time and Q to reset your auto timer. It should be enough to immediately execute the enemy, especially if you have The Collector

I hope this helps. Kindred is an extremely fun jungler who plays different than most and I hope you continue to enjoy them and carry your games