>>402195831. First gym shouldn't have 6 Pokemon, 3-4 tops. I would say 3rd gym is a reasonable place to start having full teams of 6.
2. They shouldn't be completely monotype gyms. It makes it easy as fuck to sweep and just lacks character. Give them Pokemon that fit their character AND can work as counters. Think Pokemon Stadium 2 designs. Start introducing these by the third or fourth gym.
My take on a proper Falkner would be
>Spearow [Normal/Flying] (Lv. 11)>Hoothoot [Normal/Flying] (Lv. 11)>Skarmory [Steel/Flying] (Lv. 14)Three Pokemon, I could add another if I wanted to but I wanted to avoid that. Spearow and Hoothoot are both Normal/Flying, but this is the early-game so that isn't too big of a deal, plus they can both have a different niche on the team, with Spearow being a more straightforward offensive Pokemon, while Hoothoot may try to put the opponent to sleep. Both of these are Pokemon the player has already encountered both on other trainers and in the wild, so they should be familiar with both. Also since Ledyba and Spinarak are nearby there's an easy way to counter Hypnosis.
Skarmory is his "signature Pokemon", and will be something that will surprise the character, and introduce them to the Steel type as well, a bonus for Gen 2. It's also intimidating and a perfect equivalent to Onix from the first games. People with Cyndaquil and Growlithe should have a decently easy way to counter it, while other Pokemon may have to find other tactics to beat Skarmory, such as using hypnosis themselves.
There you go, an ideal, memorable, and challenging without being overly first gym.