Watchog can be a big problem. It knows Hypnosis and Retaliate. After you defeat Herdier, it will use Retaliate, and is virtually a OHKO. Send in a weak Pokemon to absorb the hit.
You are individually training your Pokemon. Like I posted before, I tend to only use my starter for a good portion of the game. So it goes by quickly for me.
I did it with only 1 Pokemon in the 50'ies
My team was:
Serpirior.
Gigalith.
Chandelure.
Haxorus.
Zebstrika/Zekrom
Krookodile.
But i spended some money for vitamines.
It's random where it appears. Just run around a lot is all I can suggest. _-_ Also bring Repels. Once you find a shaking grass and encounter a Pokemon before it, the shaking goes away.