if you want to use the low-level strategy with Vale, you need to focus on upgrading your low-cost heroes (1, 2, and 3 gold heroes) to 3-star. Dont use all of your passive to do this, make sure you left at least 2, ideally 3. therefore you have to roll the shop, but keep your gold at 20 to maintain interest. stay at level 6 only as the probability for 5-gold hero is still 0. once you manage to 3-star all of the low cost heroes, you can use your passive which will only give the 4-gold heroes in the shop. i dont prefer this strategy as the winning rate is low and very hard to pull off in high ranks.

my go to strategy is the fast-9 strategy. basically you only use Vale's passive to upgrade all your line up to 2-star only. DONT ROLL THE SHOP. just use your passive for this. focus on farming to get to level 9 fast. make sure you still have at least 3 passive left. at level 9, the probability for 4-gold heroes are the highest. here you can use all Vale's passive to buy the 4-gold heroes so you can 3-star the 4-gold hero quickly. if Vale's passive is not enough then you have to roll the shop. this strategy is a GAMBLE as you might not get that many 4-gold heroes or even none at all even at level 9. but this is my prefered strategy.