You're not exactly looking for a career here, but you do can get good money. If you want a career, you'll need to climb up the ladder, step up your game, and go into marketing and even management in the school you tutor at.
There are three main types of teaching English abroad: Programmes or projects (eg Oxbridge Summer School, JET, etc), teaching in state schools, and teaching in private schools or tutorial centres.
With the first type you'll need to look into the requirements for individual programmes.
The second type, you will very often need a relevant degree plus a proper teaching qualification (CELTA is not one, you'll need a BEd, a PGCE, or PGDE usually; or teaching qualifications recognised at least by one government somewhere in the globe).
The third type, you will most likely need a degree. It's possible for you to teach without any qualifications, especially if you're white; but in this case there will be little job security or the pay will be bad. You're essentially a backpacker travelling around Asia hoping to earn that extra penny in this case.
After obtaining a degree, many factors are involved in what jobs you'll land yourself with: Whether it's in a relevant discipline, which university it was from (the best from Oxbridge), and whether you have additionally qualifications (postgraduate degrees > qualified teacher status > PGDE/PGCE > CELTA). And it's a combination of factors: If your degree's from Oxford, you will land yourself jobs without experience, any other qualifications, or even had the degree in a relevant discipline.
In your case, with bad GCSEs and not having a degree, you're definitely not looking into anything bright and long-term. You won't be hired to teach, with obvious reasons, school-leaving qualifications, which is the most intensive market in Asia. You could get jobs having 'chats' classes with children and possibly people of any age; you might be hired to tutor pupils who are below the age level for any public examination; you will be hired for very short modules in and out of school, eg weekend supplementary classes, drama classes. But with the last bunch, you won't be able to get a work visa with that; so you'll either get a study visa (by actually studying something there) or do it illegally whilst you're on a tourist's visa.