Pokemon match up suggestion needed

Tentacruel: IV89% / CP2015 / Poison Jab + Hydro > Pump

Ignore that guy. Just build another vaporeon, he is stronger.

Dragonite: IV82% / CP 2003 / Steel WIng + Dragon > Claw

Makes at least a good defender.

Victreebel: IV98% / CP 1954 / Razor Leaf + Leaf
Blade

Good against waters.

Exeggutor: IV91% / CP2492 / ZH + Solar Beam

Great against waters.

Vaporeon: IV84% / CP2665 / Water Gun + Hydro
Pump

Good! Get another one.

Snorlax: IV78% / CP2829 / ZH + Body Slam

Great generalist.

Rhydon: IV89% / CP2798 / Mud slap + Earthquack

Great

Lapras: IV78% / CP2156 / Ice Shard + Blizzard

Really good.

Slowbro: IV84% / CP2108 / Confusion + Psychic

Good defender.

Poliwrath: IV91% / CP2089 / Bubble + Hydro Pump

Good defender.

I would try to get someone with fire to fight grasses with, and someone with electricity to fight gyarados with. And I would try to get some additional Varporeons as cheap generalists for attack and defense. -> Go and look for some Eevees! :-)

Good luck!

All of then are good actually, but don't waste stardust on all of then. You can use it on: Lapras, Snorlax, Eggy, Dragonite, Rhydon.
Dont use it on Vaporeon because they're far too easy to obtain, so you'll have one better sometime.

By the way, try to evolve that Abra, Alakazam became a beast attacking literally anything on he game untill GenII.

Fire wise there's little to choose between Arcanine and Flareon - if candies are reasonably available locally try and get both and evolve whichever has the better moveset. Some places Evees seem really common, but round my way you'll only see a few a week and unless you've not used the naming trick yet you can't guarantee a Flareon so it might take seven or eight evolutions... Arcanines have an annoying habit of coming with bite/bulldoze in my experience...

Electric wise Jolteon is the best - I slightly prefer Thunder over Thunderbolt, but both work well. If you end up with a good Electabuzz he'll make a decent and only slightly weaker alternative (still great at wiping Gyrados/Lapras/Dragonites and Vaperons).

alot of the ones you mentioned are great defenders not attackers - something important to understand the difference. in terms of attacking snorlax - rhydon is now your best bet (along with dragonite/ alakazam or any other pokemon that dishes out quick damage. arcanine was great before the nerf).

vaporeon is very easy to kill with exeggutor- easily the most efficient vape killer - as long as it has solar beam...as is venasour/victreebell/or any pokemon will double grass. dragonite also does well vs vaporeon.

Exxegutor is also very easy to kill- anything fire will eat it...and dont sleep on scyther/pinsir as its double weak to bug

dragonite - the most ovverated defender in the game- its nice because itll put you at the top of a gym but its SO easy to kill...anything with ice will demolish it. lapras can take out multiple at a time- cloyster is also great.

advice for you would be completely ignore tentacruel (it has no business being in that list)...power up your dragonite as a great attacker just overall good pokemon to have cp - definitely power up lapras as i forgot to mention before exxegutor and any grass type is also weak to ice....so not only can you take down dragonites well anything grass doesnt stand a chance. in my opinion lapras is the best pokemon in the game. snorlax is the best defender but not the best attacker..lapras can attack and defend very well. but why not power up the snorlax...great moveset for defense. rhydon maybe a little powerup as i prefer rock smash for attacking snorlax and its not the best defender your dust can be used elsewhere. the others you mentioned are again more so defenders than attackers - but absolutley powerup alakazam full once you get one (assuming it has pyschocut)