As a proof of concept this is fine. It has potential. I suggest adding some kind of game speed up (skill or a relic e.g. speeds up movement and attack speed by x%). Also currently there's only 2 relics worth upgrading, protection and necklace.
Both speed up the game, since you either need less hits to kill an enemy or don't get stunlocked for 10 seconds
You can upgrade vampire, but I don't see a point to upgrade it past like 5%-8% since it will matter only on the first lap. After that you start scaling your stats faster than enemies.
Power is completely useless since it only affects starting damage and does not scale.
While endurance is the only way to rise max hp its far more beneficial to spend those gems on more money and buy defence to negate damage.
Your quest are a bit off, I think you accidentally set distances in meters instead of centimeters, at the point you can realistically think about grinding 100km cumulative you probably have all the upgrades you need to play indefinitely, if you wanted to. At that point getting 20 gems for your effort feels more like a slap with a dirty rag than a reward. Same goes for other distance quests. 1000m would be far more realistic and the reward reasonable.
You should add some sort of automation to this, since it starts to get annoying to buy same 7 upgrades every 3 enemies and it just adds unnecessary mouse clicks.
Potentially some sort of prestige mechanic would be an interesting addition.