id say, just for the looks you get, some of chrissy's stuff. she made some sets that finish what they started with the mountain and ricepaper mullberry windows.
Created by Chrissy6930 for
http://www.ts2creations.comyou can realy make things match up with more style with those.
i always get PurplePaws bathroom sets from mod the sims 2, she has a full set for basic bathrooms, and their only recolors, so you dont have to worry about them crashing freetime
i also get Targa's minifridge now, since it makes a lot of sence for me, i love making more room with it being under the counters.
(also mts2)
ooh, and the spiral staircases, you have no idea how much space you can save.^^
and the mini lots that marylou and co made. 1x1 thru 1x5 lots in comercial and residential....they can be a blessing for people trying to keep a sim homed without using the cash cheats