Never had more than one bike at once.
Honda CB50J (£105 without MOT.) - Did it up, Kept for a few months and a few hundred miles. Traded in once I passed my test. Wish I had kept it as there is only one left in the UK...
Suzuki GSX250 (£225). Kept for about 2 years and less than 2000 miles until mounting student debt forced me to sell. Rotted real quick, aluminimum disentigrated and electrics were awful, but it went a lot better than the similar on paper CB250N.
Honda NT650V (£3600). Kept for 3 months and 4000 miles. Nice bike but a bit big and bounced around scarily...
Kawasaki ER6F (£4200 new). Kept for 18 months and 36000miles. Perfect bike for me. smaller and easier to ride than the Deau. More fun too but that tank is much too small. Comfy upright riding position, nice beat from the exhaust. Surprisingly good wind protection from the fairing (considering).
Kawasaki 250R (£3600 new). Kept for 15000 miles and 9 months. Thought it would be cheap to run and go 2 days on a tank (which it did). However much less fun to ride than the ER6. Economic on tyres. MPG better than the ER6 but not outstanding. Insurance ridiculously high. Very cold and wet ride when not in the summer.
Honda NT700V (£6200 new). Kept for 15000 miles and about 9 months. Tyre wear and petrol consumption was surprisingly high. Lacked the sparkle of the BMW. Beautifully comfy and warm though and the only bike I had suitable for touring the UK in the winter (or in a very wet summer either).
BMW F800S (£3600 s/h). Still kept. Currently done about 20000 miles and just over a year. Not the best bike for people with Chronic Osteoporosis when in traffic (my bones ache) but good fun and a great "do everything not too bad bike." Much cheaper to run than any of the above bikes (including the 250). Belt drive is particularly good feature. Petrol tank is too small.