Hello Aspirant

With a score of 108 marks in KCET 2021 you can expect a rank around 4k-5k. This is good rank if you want to get into top colleges in first round itself.

If you want to get in BSc Agriculture then your marks for Physics, Chemistry and Biology are considered. So if you want to get into top colleges then you should have a rank below 2000. In order to get this rank, you should score more than 120 marks out of 180 in KCET if you want to get a BSc Agriculture seat in first round itself.
So as per your rank you may get top college with agriculture quota in first round only. If not wait for another round you will definitely get good college.

Hope this helps
All the best...!

For further details regarding marks vs rank go through following link;

https://engineering.careers360.com/articles/kcet-marks-vs-rank