Gap after education

I have 3 years gap after my B Tech and since then I haven’t worked for any company.Would it affect my selection?

Yes, there will be problem.
If you are 2014 pass-out and have 3 year gap, then companies will not shortlist you as they are taking only 2018/2017 pass-outs now.

Yes, it will. Considering your three year gap, you should be 2015 batch. For 2015, At Elitmus there will not be any job can check jobs section, Companies have started recruiting 2018 batch.
A free advice : Be strong on your technical and try through Walkins.
Hope it helps.