How many fighting types to power up?

I usually take out the blissey with a ho-oh, and one Machamp can handle the rest of the normals. I also switch out mon that are attacking gyms before they faint. If something goes wrong, I have four other generalist mon that I can swap in.

I have 3 machamps and 2 hari's

It was important for me to have atleast 6 good fighters, since they are not only useful in gyms, but also in a lot of Raids

Well, I have 12 strong fighters now (thanks weather update!), which comes in handy for 4* duo´s

I don't really want to power up Machamps anymore, I'll just look for 1k+ wild Machops during Cloudy weather and evolve them if I need to grow my fighting squad. Mainly I use 3 that are levels 40, 37.5 and 37. When the Regis come I'll probably look into upgrading the squad a bit, but until then these 3 are enough for my needs.

6 high IV, high lvl fighters (just machamp and hariyama) for duoing Tyranitar. For backup in case you need a second team Breeloom, Poliwrath and co at lvl 30+ wild caught will make it

gotta have an army

my go to to is a Mewtwo with cFB.

When you say power up do you mean to max? Or to thirty?

I still don’t have a max fighter, but intend to eventually have two. But thanks to weather boost I now have 14 fighting types at Lv 30-35.
6 machamps (4DP/2CC), 2 Hariyama(both DP), 2 blaziken, 1 Breloom, 1 Heracross, 1 poliwrath, and 1 primeape.

At the moment I have 5 Machamp (91%+, of which 2 100%s) powered up to the last Tyranitar breakpoint, about 4 mediocre wild caught between lvl 30 and 35, a lvl 31 98% Breloom, and a mediocre lvl 35 Hariyama. I eventually want to have at least 6 100% Machamp at lvl 40 and that Breloom too. If I ever find (more) worthy Breloom and Hariyama those will go to lvl 40 too.

In short, you can never have enough fighting types.

Try to get weather boosted machops hariyamas. You can get free attackers without investing dust. I hope your biome spawns them.

None! You can find high lvl (up to 35) and high IV Machop and Makuhitas in the correct weather conditions. Just evolve a few of those, perhaps add some TMs and you're set. No stardust!