My current team, just after getting my fourth badge, and just before the Lighthouse in Olivine:

 Feraligatr Lv. 30, Growlithe Lv. 28,

Exeggutor  Lv. 30, and Magnemite  Lv. 29.

Ultimately, I'd love to have:

Feraligatr, Blaziken, Exeggutor,

Magnezone, Honchkrow and Mamoswine.

The Blaziken will be acquired via a trade from one of my friends, and he's taking my Magnemite when it evolves to bring it to Mt. Coronet for a while. It's looking doable, the only thing I'm not looking forward to is the painful slog of Swinub to Piloswine. Alternatively, I could keep the Growlithe I have, and substitute Arcanine for Blaziken, but I would like to work in the Fighting type.

Ok, post Cianwood Gym, just got the medicine for the lighthouse, but probably going to Mahogany now.

 Feraligatr Lv. 30, Arcanine Lv. 34,

Exeggutor  Lv. 31, and Magneton  Lv. 33.

I can leave Arcanine on the back burner for the moment, he's in good shape to take out Jasmine now, so focus goes to Feraligatr and Exeggutor, to bring them up to speed.