Best way to book a quick European trip for an individual traveller?

There's booking.com

But I found getting insanely cheap flights on Ryan Air (35 euro round trip), and then browsing Hostel World for a 1 bed in a mixed bed dorm to be extremely cost efficient (like, 35 euro per night).

Basically a couple night stay at a European destination, preferred booking methods?

Open to all possibilities.

munchkin_utd

book ryanair through ryanair website, hostels through hostel world .

Were you expecting to get them cheaper somewhere else or what is the actual question ?

For your budget you need to factor in airport transfers / local transport at the destination (often day tickets make sense, but depends on the city) and if you are on a budget then also watch food and drink costs as city centres can be extortionate but eating a little out where locals are/ getting lunchtime specials / get cans from a kiosk and drink in the open can be way to save cash

z80CPU

Why not consider the "aul mailboat" OP ?

Couple of nice choices from Stena and other operators. And pay a few euro more for a nice cabin. And not as fraught passport control.