It is quite easy to get into TAFE or enrol in courses with various Adult Community Education providers. There are generally no formal prerequisites although students undergo a basic literacy and numeracy entrance test. Where prerequisites do exist TAFEs often have bridging courses to get you up to speed.
TAFE certificates and diplomas can be used as a stepping stone to university or to a career. Some TAFE courses will not accept students for a Certificate IV course without VCE but you can normally talk you way in, if not, you can sign up for the Certificate III course which will then lead on to the Certificate IV one. Up until the age of 20, students may complete qualifications at the same or lower level than others they have already completed in a different field. From age 20 onwards, funding is only available to complete a higher qualification than already completed.
Take a look at what your local TAFE has on offer. There are also many private training organisations who offer certificate and diploma courses. In Victoria, under the Youth Guarantee, students under the age of 20 who do not have VCE will receive a guaranteed place in TAFE or with participating ACE providers. To check your eligibility for a funded place see the Victorian Training Guarantee Eligibility Indicator.
Check out websites for all TAFE institutions in Victoria and all subjects that interest you. Websites for all TAFE Institutions and Independent Tertiary Colleges are available on the VTAC site
There are many ACE providers around Australia. Again, take a look around your local area or search the internet. The Council of Adult Education is also worth a look.