Can I put my opinion on this? No? Too bad. Here's my wonderful opinion. :D
Collating all the types you have on your team, it makes up:
So, what you need is a Fire-type. There are three good Fire-types that are available to where you are right now. (Lavaridge, I believe)
Magcargo has generally good stats, excelling in a 120 Defense base stat. All it's other stats are quite average, really. It also has a secondary Rock type, which is pretty good.
Camerupt is also like Magcargo, and has 100+ Attack and Sp. Attack base stats. But it's other stats are quite under-average, including an abysmal Speed. (But, a Quick Claw could fix this if you're not planning to use any other items) It has a secondary Ground type as well, however Marshtomp already has a secondary Ground-type, so if you're all about evenness this option is ruled out straight away.
Torkoal is another defensive Pokemon, having a legendary base Defense stat of 140. But, like Camerupt, has a dismal Speed stat. But Quick Claw to the rescue! :D
Out of all of these, I'd choose Magcargo, really. But it's your choice, really. They all have generally average move pools.
Now, if you want another Pokemon to add, you need an Electric-type! There are many good Electric-types out there, the primary ones being:
- Raichu (only available in the Safari Zone)
Electrode is still a rather average Pokemon, but has incredible Speed and a somewhat unique movepool if you extend it to TMs.
Magneton has a less unique movepool, but has interesting stats with a good Sp. Attack and Defense. It also has a secondary Steel type, and it's being Steel/Electric it has been titled to have the most resistances out of any Pokemon!
Manectric is a less appetising Pokemon movepool-wise with average stats, but it does stand out in Sp. Attack and Speed. This could help you quite a lot.
Raichu is a great Pokemon, but is only available a bit later in the game when you get to Mt. Pyre and Lilycove City. But it may be worth the wait - Raichu can learn some interesting Fighting-moves, and has above-average stats except for HP and Defense.
Again, you can be the judge on what Pokemon you think. But that's it - my opinion. It's completely up to you what Pokemon you choose, so choose wisely. ;)
Hope I helped. :)
Sources: Serebii's Pokedex Pages for each of the listed Pokemon.