In general, looking for the least is a bad idea. Netbooks often have a feature-limited graphic chipset and small display. PlaneShift needs rather powerful gaming hardware, much RAM, and a minimum resolution.
At least 800 px height is probably necessary to display all internal windows. Integrated graphics are much slower than a separate (dedicated) card, so intel Core i# HD, Nvidia 8k/9k or AMD/ATI HD 5k/6k should be a recommendable minimum choice. A dual-core CPU is very recommendable, as well as at least 2 GB RAM.
You know ... a game should be fun, and the fun already ends when the hardware is too weak for it. Fortunately, it seems that there are already Notebooks around 400 EUR which are potent enough.
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P.S.
Examples for Germany - at least Dual Core, 2 GB, and dedicated Nvidia – keep playing with that if you like.