When to go castle and when to stay in feudal?

I am new to the game and currently spamming franks and learning scout rush. after 6 scouts in feudal I go on a raid and usually get 5-6 vils and all

my scouts die(is it fine for them to die after i disrupt opponent's eco?)

now after this do i save up for castle or do more raids with scout and skirm/arch(now he probably has 3-4 pikemen)

also, whats the rule of thumb? how many vils before clicking castle? (no build tells this sadly)