hey,

i hope you are doing well , see the thing is that B.tech can be pursued after completing your 10+2 and polytechnic can be pursued right after your 10th standard , but here as you have mentioned that you have not secured good percentage then sorry to say but no good college will give you admission and pursuing engineering from non reputed or not good college will be i think worthless , as you have made your mind to go in engineering field then i would suggest you to first take admission in polytechnic , after completing that take lateral entry in any of the good college for the B.Tech course.

hope this helps

goodluck!