Diploma

The kind of job you get depends on your grades as well as on your interview with the company. For that, along with your studies, you need to improve your speaking skills, listening, skills your body language, dressing sense and general etiquettes. It is better to make them your habit so you will look normal.
All the best.

Babaria institute of technology, Ahmedabad institute of technology, are two top distance learning center for Engineering in Gujarat.

Hello,
As you were not able to get into a job of your field directly, B.Tech or BE is the only option for you. Only on pursuing this course, you can try your luck again in your field. If you are not interested in Engineering, then you can still continue to look for on field jobs while continuing with your current job.
All the best.

Yes, you can take entrance exams for B.Tech and since you have already done Diploma in metallurgy engineering, so you can directly take admission in the B.Tech 2nd year through lateral entry.

There are many institutes from where you can do part-time BE and if you have some work experience then you can pursue B.Tech through distance too.