Polytechnic

As per your qualification, you should look for a job.

Polytechnic will not hold any value if you don't opt for B.Tech afterwards.

ITI training in different trades varies from six months to two years. Prerequisites for the ITI courses range from 8th to 12th class pass. Its a lower qualification in comparison to Diploma in Engineering because Diploma is generally a 3 years course. Diploma in Engineering aims to provide students with industry or job related engineering knowledge, scientific skills, computing & analysis, mathematical techniques, a sound knowledge of English to communicate in the field and ability to apply problem solving techniques.
Therefore, it is recommended that you opt for Diploma in CSE over ITI certificate in CSE.

Hello Bishnu,
Almost every state has its own set of rules and procedures. Some states conduct entrance exams while others admit students based on marks of diploma. DTE if your state will give you correct picture.

Hello Yaman,
Diploma imparts skills required for job. 12th prepares you in theory. If finance is not permitting then go for diploma, get some job, or at that point in time get bank loan and complete degree.
Best wishes.

My friend,
You may see the article by the hindu newspaper about the related topic by clicking in the link given below:
http://www.thehindu.com/features/education/Advantage-polytechnics/article15913515.ece