Your combination is fine as long as you are okay with it. I don't believe in targeted subjects as long as you have prepared well. The way of writing and how you present your arguments can be targeted, not all the aspirants or the whole subject. CSS is based on individuality.
Joining academy for Essay and Precis is prudent- if you need it. For other subjects, it is your choice based on how comfortable you are studying on your own. If you feel the need for an academy, go for it. However, if you can prepare said subjects yourself, do not join academies, except for English.