I'm thinking of making my countess a melee dps / call to arms build, but what pet would i want to use for this build?

Sorry if its obvious I haven't been playing for to long lol

there are many options and I don't think there is "one perfect familiar". Here are some examples:

an apprentice squire (+tower damage) or huntress squire (tower speed) is great at NM mode to buff your towers.

a genie will help you get plenty of mana.

Animus, Unicorn and Robot (desctructiod; the "humanoid" one) do plenty of damage.

does the genie give back x amount of mana per his hit or your hit?

Your hit, x depends on his attack power

oh ok, and for call to arms of the countess do it go up in mana cost the longer you have the spell going? or does it cut out after a certain amount of time

Genie almost required if you intend to keep your buff on 24/7.
Apprentice Guardian is probably the best tower buffer, especially if you don't plan to wander too far outside of your defenses.
Devil isn't so bad either if your builder sucks with low tower health.
Other than some of the challenges I don't find DPS pets to be all that useful.

If you're just going for a traditional DPS route I would probably recommend a Fairy. Allows you to go out wherever you want and is great for Hardcore mode. Just don't jump off a cliff because the fairy won't save you from that... sounds stupid but you'd be surprised what Jousting can do.

Just my 2 cents...

I'd probably try to fine a genie i could upgrade, but will probably be a bit since i got to find a good dps set and weapon

Could also consider a good fairy, if you plan to run nightmares then you will take a huge amount of beatings due to mellee char. This is where the heal from the fairy comes handy, whilst the dps output might be lower, then you wont have as much downtime doing nothing because of low health.

So i'd say a fairy would be a good choice. (a good one)

I'll have to check them out, I got to find a good weapon and armor set to :/

I think the huntress guardian might be better than app guardian now, with its recent nerf :S