Hi there Adam,
well, the same questions come up every day. If you search a little on this site you should find quite some information already. Despite that, let me make a couple of comments:
* A few friends I knew in HK said they worked for Gaba, and Peppys kids club. Can an english teacher out there give me advice, and maybe the pros and cons for working with big companys vs small ones.*
Well, working for one of those big companies has definitely it's advantages. The job is more or less secure, they give you lots of assistance in finding an apartment and so on, the salary is (almost) the same with most of them (around Yen 250.000).
Another option would be going thru the so-called JET program. Just google or Yahoo for it, there is an official Japanese Government homepage on the net.
* In a perfect world id love to get a working holiday visa, travel japan for a few weeks or few mopnths and get a feel for the country and then hopefully travel back to an area I liked the most and start looking for potential jobs? *
If I'm not all wrong it wouldn't work like that. Nothing is perfect. You only get your working visa if you have an employer, and the respective employer decides where you will go. Maybe you should come over here as a "normal" tourist, check out the area, go to language schools in person and ask them if they can provide you with a job.
* Also....HOW MUCH $ SHOULD I BUDGET???????
For say apartment, accomodation before hand etc basic expences to set my self up in a large city in japan. *
A large city is always more expensive than countryside! Also the competition is more stiff in reference finding a job. Tokyo apartments (1 room) can run something like 80.000 to 100.000. Of course if you are looking for the action, i.e. lots of entertainment, Tokyo, Osaka and alike are the cities to go for.
Hope this helps you a little. I am sure there will be more comments.
PS: here is the URL for JET (at least one of them):
http://www.jetprogramme.org/