Blessed are the poor in spirit for they shall see God.
To be poor is to lack something. It can be something good or evil. To lack something good is bad, and to lack something evil is good. So in contrast to this, being poor in spirit means to lack something that is not required by the spirit - the Holy Spirit.
Anything the Spirit does not require is bad. Whatever the Spirit requires is good. If then lacking bad is good, then the Spirit requires us to lack all things that are not relevant for our union with Him.
The TRUTH says that no one can be good except for God. This means that we lack good, which is bad. And since the Spirit requires us to be good, we have to abhor all evil in other to attain the requirements for our acceptance as children of God.
Now, being good cannot be by our own will. We can desire to be good but without the grace of God, that desire cannot grow to produce any resourceful outcome. We can only be good when we lack bad; that is, when we are in union with the Spirit. This is because only God's children are counted as good, and IN THE SPIRIT, He the Spirit would bear witness with our spirits that we are children of God.
In all these, we can understand that being poor in the Spirit means subjecting ourselves totally to the spirit in order that we may be made what we are required to be made by God, through the Spirit that we have been subjected to - provided we believe in Him.
Being poor in the Spirit has nothing to do with money.
If a rich person already owns a house, the good kign would not get him another house, but give it to he who has no shelter. This means that you cannot expect to be good if you think you can, by your own will make yourself good. It is only by the Spirit one can be good. Without the Spirit no one can be good, because He is the owner of all righteousness.
Anyone who can see God cannot be bad. Only one person has seen God, and He is the TRUTH. The TRUTH on seeing God can testify to us what God is, and what He requies from us. And since the TRUTH is sharing His inheritance with us as children of God, he has made known to us what His Father - our Father, wants us to do. We can't be richer in righteousness than the Father who owns righteousness, and in order to attain such kind of righteousness, we must submit ourselves as empty needy souls before Him. The TRUTH made us know beforehand, that a servant cannot be greater than his Master, but can be like his master. This teaches us that being servants of God is enough for us to be like God, not greater than Him.
So we can see God when we are His humble servants, and live according to the level of righteousness that He gives us.
In my opinion, to be poor in Spirit means to subject totally oneself to the Spirit of God, and through that, one will see Him - for He God has promised to live with His chosen children in the new Jerusalem.
Grace be with you.