What blessings are promised in scripture, and what are the conditions, if any?
Here are a few:

Deuteronomy 6:1-3
1 These are the commands, decrees and laws the Lord your God directed me to teach you to observe in the land that you are crossing the Jordan to possess, 2 so that you, your children and their children after them may fear the Lord your God as long as you live by keeping all his decrees and commands that I give you, and so that you may enjoy long life. 3 Hear, Israel, and be careful to obey so that it may go well with you and that you may increase greatly in a land flowing with milk and honey, just as the Lord, the God of your ancestors, promised you.
Promise: Long life….it may go well with you and that you may increase
Condition: Observe the commands, decrees & laws….be careful to obey them…

Psalm 91
1 Whoever dwells in the shelter of the Most High will rest in the shadow of the Almighty. 2 They say of the Lord, “He is my refuge and my fortress, my God, in whom I trust.” 3 Surely he will save you from the fowler’s snare and from the deadly pestilence. 4 He will cover you with his feathers, and under his wings you will find refuge; his faithfulness will be your shield and rampart. 5 You will not fear the terror of night, nor the arrow that flies by day, 6 nor the pestilence that stalks in the darkness, nor the plague that destroys at midday. 7 A thousand may fall at your side, ten thousand at your right hand, but it will not come near you. 8 You will only observe with your eyes and see the punishment of the wicked.
9 If you say, “The Lord is my refuge,” and you make the Most High your dwelling, 10 no harm will overtake you, no disaster will come near your tent. 11 For he will command his angels concerning you to guard you in all your ways; 12 they will lift you up in their hands, so that you will not strike your foot against a stone. 13 You will tread on the lion and the cobra; you will trample the great lion and the serpent. 14 “Because they love me,” says the Lord, “I will rescue them; I will protect them, for they acknowledge my name. 15 They will call on me, and I will answer them; I will be with them in trouble, I will deliver them and honor them. 16 With long life I will satisfy them and show them my salvation.”
Promise: This is not explicitly a promise from God, but rather an affirmation of the faith of the psalmist – perhaps a subtle but important distinction.
Conditions: Again, knowing and observing the law of God.

Proverbs 3:13-20
13 Blessed are those who find wisdom, those who gain understanding, 14 for she is more profitable than silver and yields better returns than gold. 15 She is more precious than rubies; nothing you desire can compare with her. 16 Long life is in her right hand; in her left hand are riches and honor. 17 Her ways are pleasant ways, and all her paths are peace. 18 She is a tree of life to those who take hold of her; those who hold her fast will be blessed.
Promise: blessings, long life, riches and honor
Conditions: Find Wisdom, take hold of her, hold her fast.