HI JC
Firstly I got back into my old clothes. Then I started buying from Charity shops or EBAY only - no point at all buying brand new as you will go out of them so fast.
I created a system of staged sizes. Current, next size down and then a size down from that. I kept two large plastic bins at the foot of my bed which I filled with the smaller sizes...sort of a staging area.
Then each week I would try on stuff in the closet and set aside what got to big, then worked through my bins. shifting from one to the next as the sizes either fit or got closer.
It was so fun, it was always a surprise seeing what went on next and seeing what I thought might never fit move closer to the next "stage". It was very satisfying and motivating.
I found GREAT clothes in the charity shops. Next, Per Una, Karen Millen, Liz Claiborn, etc., for a mere few quid, and all pretty current, so I basically replaced my entire wardrobe on the cheap. Got a lot from EBAY as well.
Have fun!!