By now most trainers have expanded both the contents of their Pokedex while honing their particular favorites, although developing a team specifically geared towards battling can be a whole separate story. The combined tasks of defeating, capturing, and then holding gyms can be particularly daunting; regardless of one's trainer level. The following tips will hopefully help improve both your rate of success in battle but also your experience with gyms in general.

Regardless of the fact that there's 151 Pokemon in Generation one (145 currently available) many gyms at this point consist of often monotonous lineups including but not limited to the following Powerhouses:

Tier one:

Dragonite, Snorlax, and Lapras

The ever elusive and all the more powerful Dragonite dominates both in it's offensive and defensive capabilities. Being part of the only dragon-type evolution line available in generation one Dragonites are only particularly weak to two matchups: other Dragonites and powerful Ice types, namely Lapras and eventually Articuno.

Snorlax is an all around monster much like Dragonite; although Snorlax's only type-based weakness comes in the form of Fighting-type attacks. It's worth noting that the current best Fighting pokemon available, Machamp, ultimately is out-performed by Vaporeon against Snorlax as concluded by youtube user 'Trainer Tips' in the video below:

Next among the best of the best is Lapras, if you're lucky you've perhaps caught this Water/Ice type behemoth or if you're even luckier still then you've hatched one. Lapras not only excels at holding down gyms with ease but it's also the one surefire counter against Dragonite. While being susceptible to fighting rock and ground-type attacks, Lapras also boasts bonus ice damage against both rock and ground-types (among several other types.)

For the record one might also consider Vaporeon to a Tier one pokemon given it's insanely high HP and CP, not to mention the fact that it's insanely easy to obtain. To add to it's power Vaporeon only comes equipped with water type moves, just as Flareon and Jolteon both only come equipped with fire and Electric movesets, respectively. Vaporeon is more than just the most powerful Eeveelution, it also has a natural proclivity towards incredible stats and an even more incredible ability to wash away even the most tanky of pokemon regardless of their type.

Tier Two:

Although the second tier is much less set in stone than the first, the following Pokemon can hold down a gym or even pull one down without breaking a sweat:

Arcanine, is my personal favorite among Generation one Pokemon and it also happens to be my Pokemon with the current highest CP at a whopping 2242. So long as you're lucky enough to evolve or perhaps even catch one equipped with fire fang along with either fire blast or flamethrower this canine is certain to be among your best of friends. Personally mine has been the second highest of 10 Pokemon in a local gym for upwards of three weeks and I'm beginning to miss my furry-flaming-friend, as his ability to out DPS just about any other Pokemon whose name doesn't begin with "V" and end with "Aporeon"

Next comes a Pokemon many players (myself included) overlooked in the former games.

Exeggutor, this psychic and grass type may appear a tad bit ridiculous but in Pokemon Go he packs a powerful punch against some of the games most common defenders; AKA Vaporeon. During my recent trip to Virginia I happened upon two wild Exeggutors both equipped with solar beam and startlingly high cp, although as it turns out they both have laughable IV's. Regardless of their IV-handicap these two have been more useful than just about any other single species of Pokemon thus far.

This next slot belongs to the mighty Gyarados, despite requiring the most candies of any other evolution 400 Magikarp candies, this fearsome creature can also roll one of the single most disappointing move-sets of out of any other; Bite and Twister... as mine did. If you happen to obtain this Deep sea beast keep in mind it also boasts a flying type somehow, thus making it all the more susceptible to electricity, but seriously does Gyarados have gills or what's the deal?

Tier 3:

Beneath these heavy-weights is the third and largest of the major tiers. This third tier boasts many of the more conventional crowd-picks like Blastoise, Charizard, Venusaur, Slowbro, Nidoqueen and Flareon, but also contains some choices that are often underestimated like Poliwrath, Wigglytuff, Vileplume, Victreebell and Golduck. Many of these Pokemon can be used interchangeably with each other for a devasting effect. For the record I would love to be able to include Alakazam, Raichu and Ghengar in this tier or above but as of right now these high offense/low defense based choices are brokenly underpowered even at their maximum CP, with optimal IV's and even optimal movesets. Even at Trainer level 29 my Raichu maxes out around 1600~ CP even with 92% IV's while my 94% Alakazam can reach a meagre 1500~ despite requiring some extraordinarily elusive candies.

Tier Four:

The Fourth Tier is even more malleable than the Third, however it currently contains many of following Pokemon with limited strength yet also easily exploitable weaknesses. Rhydon, Nidoking, Jolteon, Ninetails, Rapidash, Clefable, Dewgong, and perhaps even Raichu. Mainly specializing in offense these choices can exploit the weaknesses of many typical defenders while being subject to similar ends when used defensively themselves. The phrase "pick your battles" holds a great deal of weight among Pokemon of this tier.

Any particular Pokemon's strengths are ultimately relative to how they are implemented and who they are facing up against. Given this subjectivity, a pokemon of tier four or below can potentially beat more competitive opponents under the right circumstances, as teamwork alongside proper understanding of the "rock paper scissors" style typing that truly defines in-game combat. I.E. If you come upon a friendly gym with two Vaporeons you might want to consider adding a proficient Flareon, Arcanine, or Charizard to offset Vaporeons weakness to grass attackers; as opposed to adding your favorite Vaporeon to the mix. Wheras if you're assaulting a gym composed of a Snorlax, Dragonite, Poliwrath, and Gyarados you'd better bring a solid Vaporeon to batter down the Snorlax, your best ice-type to counter Dragonite, Exeggutor to doubly counter Poliwrath's Fighting and Water typing with Psychic and Grass moves, and finally your best electric types (don't be ashamed about bringing multiple Jolteons just in case) for that ever powerful Gyarados.

While attacks like Hydro Pump, Hyper Beam, Solar Beam, and Fire Blast some of the highest damage they are always relatively easy to dodge. Due to this dodging is more than just a side aspect of battling as it ought to be considered a priority when facing many of the game's heivyweights. Succesfull dodging requires a good amount of practice but once you have even a slight grasp of what certain moves look like/how long they take to actually dish out damage you can routinely avoid up to 75% of their damage output and in so doing level the playing field. In my experience attacks like Earthquake, Petal Blizzard, and Dragon Pulse can be particularly hard to avoid, both because they sometimes initiate before giving any kind of warning and leave players to have to guesstimate when they're coming.