I live in a 3 bed terraced with my hubby and we have SOOOOOOOO much clutter, both spare rooms were so messy and you couldnt open the doors in either. When I found out I was pregnant, we had a HUGE clearout. Literally all pre-op clothes went to friends or charity shops along with a few bits on ebay...all old furniture went on the for sale or swap sites on facebook (GODSEND!!!) and everything else went in the bin! We managed to condense it down to 1 rooms, and in there is literally only things we need (suitcases, spare wardrobe, photos etc)
De-clutter is the biggest space saver...have a matra...if you aint used it within the last 6 months, year, 2 years etc...get rid.
As for actual storage solutions - the vacuum bags are always good. A little bathroom shelving unit for all the clutter within there. Boxes decorated to co-ordinate with each room etc.
Good luck! xx