Lucknow

Both are good. But SRM, Chennai has a plus point in terms of placement and infrastructure. And, it is also a reputed private college in India.

Yes, 450 marks are enough to get admission in IET, Lucknow.

I would suggest not to concentrate more on the cheaper colleges. I agree, these days, the cost of education is very high. You cannot get affordable and best colleges together. The cheaper colleges are not good in terms of faculty campus and placements. The expensive ones are much better.
You can go for DU and JMI colleges in Delhi. They have comparatively lesser fee structure as compared to the private one.

Ramswaroop College, Lucknow is a good college.

Hello Saurabh,
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Dear Riya Sharma, You should go at Made easy for GATE preparation as they have good word of mouth all over the India. I went through their facebook page. The result which was posted there was awesome. Also, study material, online test series & doubt solving sessions are the key highlights of their course
The second choice is GATE Forum.

If you are taking a admission in Delhi to take admission in Ambedkar Institute of Technology which is the best college in Delhi and if you taking a admission in Lucknow, it will be better if you take admission in government Polytechnic, Lucknow which is best college.