ssc chsl
Hi dear, first of all I would like say you Best of luck for you better & bright future. let me clarify you some facts about CHSL. Actually this is 12th level exam so it is being considerd that if a candidate gets good marks in 12th board exam then he/she will surely qualify the exam but the truth is that every exam(whether competetive or non competetive) needs a lot of practice. For practice you have to devote your time and you had to study the pin pointed topics. no need to study a lot of like daily news paper for current affair and bla-bla.......Please follow a book of your choice/recommended and try to solve again and again....here are some books that I would like recommend....
Maths-Kiran 9200+ english/hindi version
English-MB Publication or A mirror of common error
GK- any decent book
Reasoning- you have to solve 40-50 questions daily for practice from any where
If you can do this by yourself then no need to have coaching and if you can't make your routine then on join and this totally depends on youonlybut in my opinion no need to join coaching.