MUI doesn't count. It is considered part of the system.
Install SystemPatch
http://web.tiscali.it/ziosante/ right after FBlit
http://www.tpec.u-net.com/ and throw away BlazeWCP, FText, CopyMemQuicker and possibly other patches. Just read the manual.
MCP is a very good idea but not the latest version as it is very buggy. Prefer to install the Aminet version or at least an early version from the MCP website.
For less memory fragmentation i suggest MemOptimizer and FragCure installed after it. Get them from Aminet.
As others suggested, download BlizKick, have a good read at the manual and install it with some of the included modules that you will find useful. Then install Exec44. Both are located in Piru's website.
Iirc, FastIPrefs is only useful if you don't have OS3.5+
Executive is good, specially if you tend to run many programs at the same time. If you don't, it's better not to install it.
HappyEnv is highly suggested. Read the manual and try it!
Imho, and as SuperTurbo said. PowerIcons, birdie, VisualPrefs and the rest of the eye-candies is a wonderful way to waste system resources. (Mainly memory and CPU cycles)
