What Jesus means is that you will not go without what you need. Take a look at Matthew 6:25-32 I'm primarily focusing on versus 31 & 32.
"So never be anxious and say, ‘What are we to eat?’ or, ‘What are we to drink?’ or, ‘What are we to wear?’ 32 For all these are the things the nations are eagerly pursuing. Your heavenly Father knows that you need all these things."
You can pray for all sorts of things like strength, wisdom, discernment or good judgement, patience, his holy spirit.
Here is a way of illustrating the situation. Imagine God is your friend. This friend would do anything to make sure you did well. Your friend has the means to do anything or buy anything. What happens when you start using that friendship to gain money and valuable things?
What you ask for shows your motive. If you ask for things that help you keep Gods commandments then he will indeed bless you. If you ask for thing out of desire for personal gain selfishly then God will ignore your prayer.
Look at the example of Jesus. He owned nothing, but the clothing he wore. Another guiding scripture is yet another verse from Matthew 6:19-21:
“Stop storing up for yourselves treasures on the earth, where moth and rust consume and where thieves break in and steal. 20 Rather, store up for yourselves treasures in heaven, where neither moth nor rust consumes, and where thieves do not break in and steal. 21 For where your treasure is, there your heart will be also."