Thanks for the warm words regarding one of my shops 🙂 Interesting because, since a few weeks I am no more that convinced, that my site is super fast or well designed ^^ But ok maybe I am just too ambitious. I am thinking of completly rewrite "my" theme. I believe, there is still room for improvements 🙂
Actually @Traumflug said everything, that is relevant:
Get a serious hosting package. We have a dedicated server (unmanaged) and pay 70$/month. If you can't afford this, you have probably more important things to improve, than the loading time.
Technically I use css/js caching and APC server side caching. Full Page Cache is completly deactived.
Deactivate css and js caching in Bo. Use browser console and check which files are loaded. How big are they? Are they really needed?
Check your Content. Do you really need the tags on left column? You really need to promote your local store there? For external modules, check them with profiling in BO, how much they slow down...
Defer images, if they are below the fold
In general I would say, that the page loading time is one of the strengths of thirty bees.