Dera aspirant,

You are eligible To opt for diploma only if you have completed 10 class with minimum 35% marks in both maths and science. Then you have To clear entrance test conducted by your state board and choose the college and stream you want To pursue your diploma.

For Gujrat in particular,  there is no entrance exam ,but the candidate's section is based on the following 3 patterns
1.SSC
2.TEB
3.ITI

Hope it helps you:)

Hey Gami,

In gujrat, there is an exam for diploma admission known as Gujarat Diploma Admission. By giving this exam you can get admission in diploma in the colleges you will get with you marks. The counselling registration- cum-application form of Gujarat Diploma, also known as Gujarat Polytechnic, starts from the first week of June. Please note that there will be no entrance exam, as admission will be based on marks obtained in SSC, or performance in TEB or ITI. 

Gujarat Diploma Eligibility Criteria are 

• The candidate must have passed the qualifying exam with minimum marks as prescribed by AICTE from time to time, from: 
• Gujarat Board
• CBSE or CISCE or the International School Board or NIOS or Sanskrit Pathshala. 

Provided, the institute the candidate has studied at is located in:

• The state of Gujarat.
• The Union Territories of Diu, Daman and Dadra Nagar Haveli and whose parents are origin of Gujarat
• The candidate has done schooling under Jawaharlal Navodaya Vidyalaya Scheme up to class VIII in an institution located in the State of Gujarat.

For more info about the exam visit https://engineering.careers360.com/articles/gujarat-diploma-admission

Hope that helps 

all the best