Hi, Im level 20 and reached to league 4 with 6533Hp, So I dont know about league 1 or collosseum,
But I have the same issue,
1- Pirate Silver make your hole event rank (and reward) improve, but its better than remain for next event or can change with key
2- If levelUp rewards gem is this much (50 as you said), I wont levelUp anymore till Hooligart increase it,
3- about silver coin could better if all boxes have it, like free box, 5 complit tower (blue) box and all mission boxes,
4- At the end, I think people like you that help creators to improve the game deserve some gift at game,
Have a great time