The order of the actual installation doesn't matter for Sims 3, but it did for Sims 1 and I think Sims 2. But regardless of the order you installed them, you will still need the most recently released disc.
For example: If you had the base game and Fast Lane Stuff, you would need to use the FLS disc. If you then got World Adventures, Ambitions and High End Loft Stuff, you could install them however you choose to (and it won't cause any issues), but you would still be using the Fast Lane Stuff disc since it's the most recently released expansion of the ones you have. However, if you then got Outdoor Living Stuff, you would have to use that disc instead of the FLS disc, since OLS is more recent.