Ruriko, I'd suggest asking your self the following questions before deciding on the type of the package to go for:
-are your sites mission-critical? in a shared environment there's always a risk of being affected by the neighbouring sites;
-will you need any software applications not offered by your host? only dedicated or vps paclages will give you this possibility;
-are you planning to upgrade your server? the upgrade possibilities will be limited in the shared environment;
Ask your host about it as well, usually hosts offer upgrades to a bigger plans, probably, a VPS plan might be your next step. I'm with Serverpoint.com, they offer managed VPS plans, you may look into them.