My suggestions of a basic components stock


resistors:
E6 1R-4M7 1/4W, 5%, carbon or metal film 2%. ~20eur
E12 if you have the money. ~40eur
50 to 100 pcs. each value. 
(Hint: reserve place for E12 in your storage system).
take at least 100 of E3 100R-1M, you will need those values most often.
E3 alone will do for a start if you are a tight-ass ;-). ~10eur

potentiometers: 100R 500r 1k 10k 100k 1M 5ea. ~10eur

capacitors, ceramic:
E3 10p-100n. ~20eur
I have E6 and that are more values than you really
need. Capacitor tolerances are very big. The cheap stock here
would be 100p 1n 10n 22n 47n 100n. ~8eur
You don't need many here, 
10-20 each value are plenty. 100n are often used as bypass
in digital logic, so you will need a lot of those, but then
you can get them from "cmos graveyards" in old PCs.
You can use plastic foil caps instead of ceramic most of the time.

capacitors, electrolytic (Al):
E3 1u-100u, 10-20ea. ~10eur
You will need bigger values (1000u, sometimes 10000u) for power
supply filter capacitors but you can take them out of old stuff.
I have a big percentage of desoldered electrolytics, against general
advise not to re-use them. I have a ESR meter (easy to build) and check
if they are good before using. 
You will also find tantalum capacitors, they look like a ceramic drop.
they are required sometimes, keep them.

transistors:

low power, 100mA max. collector current, to92 case:
npn (e.g. BC547) 20+pcs. ~1eur
pnp (e.g. BC548) 10+pcs. ~1eur

medium power, 1A to 4A max. collector current, TO220 or SOT32 case:
npn (e.g. bd135) 10pcs. ~2eur
pnp (e.g. bd136) 5pcs. ~1eur

darlington:
npn, pnp if you want, can be useful but can be replaced by two
of the above. TIPxxx are darlington.
e.g. TIP137 5pcs. ~3eur

FET:
A higher current version around 10A current and if you want
a small to92 version too. not strictly required.
e.g. BUZ10 5pcs. ~5eur 

linear ICs:
7805 5V voltage regulator 1A, 5pcs. ~3eur
LM317 adjustable voltage regulator, 3pcs. ~2eur
LM324 quad opamp 10pcs ~3eur
LM339 quad comparator 5pcs ~2eur
ne555 timer/oscilator 5pcs ~1eur

optoelectronics:
LEDs red, green, 10pcs each. ~1eur
LDR or phototransistor if you want.

standard logic:
??
hard to suggest anything, there are so many.
best desolder them fom old pc boards, 74xxxx.

total: ~85eur

I'm sure i have forgotten something important ;-)

ST