Clipless pedals
Clipless pedals, such as SPD, are worth recommending indeed. You may consider those snobbish, but those who have tried SPD's will probably share my opinion. The possibility of establishing optimal foot position, and the rigid sole do make a difference during long travel. A major disadvantage of this solution is its price. Clipless pedals cost around PLN 150, while the shoes – something between PLN 150 and 250. If you cannot afford SPD's, at least try to wear shoes with rigid soles while cycling, so that your whole foot can work – not just the part touching the pedal.