How much do you want to spend per month?
You can live there in a tent for so little it hurts to think about it. Or you can live in a dorm or private room and drink and party and eat out every day.
In a tent for most of the time, you can go on as little as maybe USD 1000 per month and not have to worry about how much you drink or eat. I've seen guys do it for USD 500 a month, and I've seen guys have a hard time with USD 2000 per month. Realize that it's MORE expensive to live there IN A TENT temporarily in a "camp" than it is to live there in a room/apartment/house after you get hired, and you will live (almost comfortably) on USD 1000 per month once you're hired. So, don't rely on USD 500 a month, you'll run out of money... but you can do it if you are VERY VERY VERY VERY VERY tight with your money - but then you won't be able to buy anyone a drink and you will be known as a skinflint.
You won't be paying for medicals, or exams, or conversions, or anything like that UNLESS you're hired, so don't worry about how much that will cost. Burn that bridge when you get to it.
You must be prepared to stay for more than 3 months though, even though you will only get a visa for 3 months, you'll be paying to live there (or in a neighboring country while you wait) for more than 3 months - that's the way it's been for just about everyone hired in Bots and Nam for the past few years. Some have even gone back home for a few months waiting on visas.