
avr |

Air or aether kineticists can just fly everywhere from 6th level. Before then, the strongtail alt racial trait and maybe a potion of longstrider could provide tactical mobility, and a horse with a fancy saddle should be able to carry them from place to place.
Though a small race with a con bonus (like gnomes) gets about the same stats as a medium race with dex and con bonuses, as far as kineticists are concerned. You've got more options than merfolk and hobgoblins even if you're seeking perfect stats.

The Sideromancer |
Normally, ranged requires less movement, so you might only need Strongtail (which should be standard if you aren't expecting to be underwater 90% of the time). I've built Melee merfolk for land campaigns that did fine, but I used class ways of boosting move speed to get to 25. If your group is less likely to hang around 20 move (dwarves or standard with unmitigated armour), you may need more.

PossibleCabbage |

Caligni and Hobgoblins are the traditional choices for "perfect stats" kineticists, but the Kineticist is probably one of the better classes to play a Merfolk as since it has built-in mitigation for the whole "you are bad at walking" thing. Plus you're a ranged class that can be a little tanky so "you can't run away well" isn't a huge deal at low levels.
Air is *probably* the best choice, because I *think* Wings of Air should work with Mobile Gathering, so you can gather power and move more than 1 square. If this doesn't work, I'd be inclined to go Aether first for the good defense and the level 6 flying. You could maybe spin earth into air if you're willing to wait until level 10 for the best flying.
It might be funny to play a melee oriented merfolk Kineticist (not necessarily a knight) who zips around the battlefield using blade rush to move around (since you move 30' instantly), but this will be rough before you can do it for 0 burn at level 3.

Lady-J |
Humans can get +2 to any two stats if you forsake the feat....just saying'
two +2s are not worth a feat and your skilled trait it would only be worth it if you got to pick weather you dropped one or the other, plus already played the character cant swap out, now i'm just looking for kenetisist specific things to help boost the character with their class features eventually, preferably boost to their blasts

graystone |

Play a merfolk with strongtail and take the aquakineticist. 2nd you gain waterdancer [slipstream] that increases your land/water movement.
At 2nd that makes your move on level ground 25', downhill 35' and uphill 15'. [and +20 to your swim to make back what you lost to strongtail]
Another option is Wildling + wildling stride: At third, that's a 25' movement with strongtail. [or combine with the above for more movement]
Now I want to play a merfolk kineticist.
It would be tough early on, you're pretty slow, even with strongtail your party might get annoyed that you're slowing them down.
You're better off than an oozemorph! At least the generic merfolk can move 5'...

graystone |

Waterdancer is a 3rd level Wild Talent, which means you can't take it until 6th. Which is the same level you could get "Always Be Flying" if you were an aerokineticist. Slipstream might be better if you were going to be underwater a large portion of the time though.
the archetype, aquakineticist, gives it to you at 2nd...
"At 2nd level, an aquakineticist gains waterdancer as a bonus utility wild talent".

PossibleCabbage |

In terms of kineticist items, you mostly buy stat boosters, defensive items, and general utility stuff. You can get slightly ahead of the curve since you never want weapons or weapon analogues.
Mobile Gathering is probably sufficiently useful to slot in with the "feats all kineticists should consider": Weapon Focus (Kinetic Blast), Iron Will, Precise Shot (and PBS), Weapon Finesse, and Toughness. Beyond that, I mostly just take Extra Wild Talent a lot, but I haven't played a Kineticist since Kinetic Invocation became a thing (though the options don't look super impressive except for Etheric Shards? Perhaps I'm mistaken).

avr |

No such weapon I know of. There is an (overpriced) infusion which gives an enhancement bonus to blasts.
Avoron's right about potions of course, a potion of expeditious retreat or two is worth keeping around at low levels though.
Edit: At high levels kinetic invocation may be worthwhile for wind walk, there's a real lack of good higher level wild talents. I could see taking it for many of the elements (not wood) late. The lower level air talents it makes available are especially unappealing though.