The safety dweeb in me wants to point out that flash capacitors can seriously stun the unwary. Even my little shoe-mount model made my arm go numb for a few hours when I didn't let it discharge fully before mucking about with a soldering iron. Caveat mendor.
If you are really on a tight budget the hammerhead flashes with guide numbers in the 35-45 range (iso 100, distance in meters) are cheap and plentiful on the used market, and the more modern ones will even give you ttl operation with suitable cameras - or at least auto operation with a built in photocell. You can use several together for more power and rig battery packs for faster recyling or more shots.
Otherwise, for two-three hundred euros you should be able to find a single good used monolight of around 400-500 Ws. Or a new entry level light from a premium manufacturer like the Elinchrom D-lite series. Or a "Studiopaket" made up of a couple of low power strobes from one of the many generic cheaper brands. The problem with used flash units is provenence: unless you know the seller personally you have no idea how much they have used and/or abused the system.
A lot of people justly recommend the Alien Bee units from the USA, but I can't be bothered with using a transformer: models powerful enough to run a strobe without complaint are not exactly portable.
If you want battery operation the only cheap options are to run a monolight off a UPS or rig your own battery and converter; but this gets expensive fast if you go above 400 Ws or so. Used Lumedyne or Quantum units from, say, KEH in the USA are a great bang-for-the-buck, but there is little local support and the cheapie softboxes and other light modifiers you can find in Europe won't fit without modification. There are also a couple of generic companies selling small monolights which will work off a dedicated power pack or the mains AC voltage, (see
here and
here, but they may be marketed under different names in Austria) but they are quite a bit more expensive than a simple monolight, and they are so new that I have not been able to find any reviews at all, much less technically competent ones that compare them to more conventional strobes.
FWIW, unless a Profoto AcuteB drops into my lap for pennies, I'm probably going for the Elinchrom D-lites.