Clearing the shader cache is only required once, if the game content changed considerably since you played for the last time. While there was no art update, it should not be necessary and even useful anymore.
Stating that the PC has "higher specs" is not really helpful; it would be better to know the facts in detail, most important is the graphics chipset and the driver version, but also the amount of RAM and the type of CPU is important. In general, do not rely on graphic drivers installed by Microsoft Windows (original during Windows installation or via Microsoft Update), because they may support only Direct3D well, whereas PlaneShift uses the OpenGL 3D API. The manufacturer of the graphic chipset, mainboard, or the whole system in case of a laptop, should provide a driver with complete support of graphic features. Similar advice for Linux: Depending on the graphic chipset, the proprietary closed-source drivers may support features better and more complete; but OpenSource drivers should already be reliable enough as well (e.g. 'nvidia' is quite certain to be good, but 'nouveau' shall be suitable as well, I was told).
I don't know what a "game booster" shall be. Games usually run better with less "software debris" installed.
A quite common reason for crashes is the filling RAM while you travel between different maps. Depending on the setting of the "Background loader", the system tries to pre-load and cache a different amount of content of the adjacent maps while you pass a map-loading portal in game (e.g. the Hydlaa-East passage, or the forest junction). If you select no background loading, loading a map takes a lot more time while passing the portal, but won't load much content anymore while traveling, that may make the experience more stable.
If you have a 64-bit OS, you can test if the 32-bit client or the 64-bit client runs better. The 64-bit client can use more RAM and can avoid better possible crashes by running out of free RAM while loading a map, but requires a 64-bit version of your OS. In general it is a good idea not to run much other software in the background while playing a game. Even disabling a resident antivirus module before playing may help.
Disabled sound can be a reason for a crash too. It was once; not sure how well this has been fixed. Setting the audio in the launcher to "OpenAL" is still recommendable.
Playing the game in full-screen mode should be quite safe now. But it may be more convenient to play in windowed mode instead. It may be a little annoying that you have to select the aspect ratio first before selecting a desired resolution; if you edit a configuration file manually, you can even set up almost any size just a little below your desktop resolution (preferably multiples of 16 though) to get an "almost fullscreen" window.
