I am preparation after plus two UPSC
You prepare UPSC after plus two means you plan long term, UPSC needs graduation first, so after college you can give exam for civil services,So now you finish plus two you can join graduation course like BA BSc BCom where you get good foundation, then after graduation you prepare for UPSC prelims and mains.You see career path and timeline details in this Careers360 page
https://www.careers360.com/courses