Welcome to androidforums,
Since you are not rooted, there is very little you can do about the extremely low ACE's internal memory.
The app2sd app mackinon has mentioned will be of very little help, although its all thats available for you. Since most of the apps require phone details access permissions, they are supposed to be installed in the internal memory and the apps that don't require these permissions can be easily installed in the sd card(these are the only ones you can move right now). But as you have seen the ACE has very low internal memory, hence that limits the number of apps(requiring phone space) you can install.
But if you really want to move ALL apps to the sd card, it is possible via rooting, you can use your sd card as internal memory and install as many apps that you want, but yes that will void your warranty, so its all upto your choics.
Samsung GT-S5830 Galaxy Ace
ROM: AOKP 4.2.2
Scripts: CronMod INT2EXT4+
245MHz - 800MHz, SmartassH3