can I start preparation from 1st year civil engineering for SSC CGL? what are books needed

You can prepare for ssc cgl exam anytime. You can even start when you are in final year. Ssc cgl exam is not though. You can crack if prepare 6-12 months before ssc cgl exam. There are 4 sections in ssc cgl exam G.s. you can refer Lucent. English you can read Neetu Singh. Reasoning you can go through Kirans previous year papers and for maths you can refer Previous year or even Rakesh Yadav .so its upon you, you can start for cgl anytime.