Imo GyaraJolt is extremely overrated. Jolt is terrible at baiting EQs, since Lax/Taur frequently prefer to click Normal STAB, meanwhile Don can just click RSlide if it thinks an EQ resist is coming. Offensively they do a reasonable job of supporting each other most of the time, but are both susceptible to being hard countered so this is fairly iffy (Don and Star on the same team is very plausible lol). The best teammate for Gyarados is easily Gengar.
Personally I'm not super fond of Gyara, it struggles too much against Starmie, also the Elec weakness is very relevant against Chansey as well as Star. That said, E1 is not that high a bar to clear, so I'm not opposed to it moving up.
I personally haven't played much with Tentacruel, but clearing special attackers in order for it to take on Tauros isn't the approach I'd take, purely because it's just not a good matchup for it. Also Tenta's not that bad against special attackers, it does have an Ice resist and excellent special bulk after all, but it struggles mostly against faster pokemon. Granted faster pokemon and special attackers have considerable overlap, but if you're targeting stuff like Egg and Bro to support Tenta (idk if you are), I think that's not ideal
Personally I'm not super fond of Gyara, it struggles too much against Starmie, also the Elec weakness is very relevant against Chansey as well as Star. That said, E1 is not that high a bar to clear, so I'm not opposed to it moving up.
I personally haven't played much with Tentacruel, but clearing special attackers in order for it to take on Tauros isn't the approach I'd take, purely because it's just not a good matchup for it. Also Tenta's not that bad against special attackers, it does have an Ice resist and excellent special bulk after all, but it struggles mostly against faster pokemon. Granted faster pokemon and special attackers have considerable overlap, but if you're targeting stuff like Egg and Bro to support Tenta (idk if you are), I think that's not ideal