Comme j'ai pu voir sur un ou 2 sujets : oui, il faut augmenter le niveau des opérations le plus possible au début. Au début ca peut s’averer dur, mais l’investissement vaut le détour.

Je pensais qu'il serait bien de mettre le coût pour monter de un niveau d'opération :
Level 0 to 1 operation upgrade --> +5 % XP (cost 25 gems)
Level 1 to 2 operation upgrade --> + 5 % Credits (cost 25 gems)
Level 2 to 3 operation upgrade --> + 5 % Completion Speed (cost 50 gems)
Level 3 to 4 operation upgrade --> +5% Credits (cost 50 gems)
Level 4 to 5 operation upgrade --> +5 % XP (cost 75 gems)
Level 5 to 6 operation upgrade --> +5% Completion Speed (cost 75 gems)
Level 6 to 7 operation upgrade --> +5% Credits (cost 100 gems)
Level 7 to 8 operation upgrade --> +5% XP (cost 100 gems)
Level 8 to 9 operation upgrade --> +5% Completion Speed (cost 125 gems)
Level 9 to 10 operation upgrade --> +5% gear chance (cost 125 gems)
Level 10 to 11 operation upgrade --> +5% gem chance (cost 150 gems)
Level 11 to 12 operation upgrade --> +5% Credits (cost 150 gems)
Level 12 to 13 operation upgrade --> +5% XP (cost 200 gems)
Level 13 to 14 operation upgrade --> +5% Completion Speed (cost 250 gems)
Level 14 to 15 operation upgrade --> +5% gear chance (cost 250 gems)
Level 15 to 16 operation upgrade --> +5% gem chance (cost 250 gems)
Level 16 to 17 operation upgrade --> +5% Credits (cost 250 gems)
Level 17 to 18 operation upgrade --> +5% XP (cost 250 gems)
Level 18 to 19 operation upgrade --> +5% gear (cost 250 gems)
Level 19 to 20 operation upgrade --> +5% gem (cost 250 gems)

Ce qui nous revient a un total de 3000 gemmes... Autant vous dire qu'il faudra pas être pressé pour les atteindre si on ne le fais pas dès le début du jeu

Au total on aura ces stats :
20% Completion speed
25% XP
15% Gear chance
25% Credits
15% Gem chance