Every girl shud make cleansing, toning, moisturising a daily routine..and scrub 3 times a week..if it's a mild scrub it can be used everyday as well.
Mmkaki, I've answered u're question..a concealer will hide u're marks and imperfections as well as conceal u're dark-circles. if u have flawless skin u don't need any however, if u have marks then u wud need one closest to u're skintone. That is followed by foundation and then loose or pressed powder!
Read foundation 101 please