There has been a lot of good discussion about our Blessed Mother, but since the OP also asked about purgatory I thought I'd share a few thoughts on the topic.
Let us first begin with a few verses from Pauls first letter to the Church of Corinth on the topic of Purgatory.
1 Corinthians 3:11-15:
For no other foundation can anyone lay than that which is laid, which is Jesus Christ. Now if anyone builds on this foundation with gold, silver, precious stones, wood, hay, straw, each ones work will become clear; for the Day will declare it, because it will be revealed by fire; and the fire will test each ones work, of what sort it is. If anyones work which he has built on it endures, he will receive a reward. If anyones work is burned, he will suffer loss; but he himself will be saved, yet so as through fire.
The above verses make it clear that it will be a serious purgatorial event when we meet God face-face, but let me come back to them later.
First and foremost, lets consider a few teachings of Christ. As Christians we are to follow Jesus command to do our best and follow His example out of love and obedience. He said, If you love me, keep my commandments (Jn 14:15) and be perfect, just as your Father in heaven is perfect. (Mt 5:48) This is a tough task, but that does not mean we give up in seeking holiness because we fall-short on the road to God. The Apostle Paul also speaks of this pursuit of sanctity in his epistle to the Hebrews, when he states we must pursue holiness, without which no one will see the Lord. (Heb 12:14) Did you see that last part? It says without holiness no one can see God. Now, flip over to the last book of your bible and look at Revelations chapter 21 which speaks of the New Jerusalem i.e. Heaven. We are reminded again that there shall by no means enter it [Heaven] anything that defiles, or causes an abomination or a lie (Rev 21:27) These verses makes it very clear that only things that are holy will be allowed entrance into Heaven. That leads us back to the verses from 1st Corinthians that I began this post with. In that statement to the Corinthians, Paul makes it very clear that although we can be saved in that Day, we should expect to be tested. If we have profane works i.e. sins that are burned up during the testing we will suffer loss
as through fire. This is what is meant by purgatory. It is a process to prepare us for sin-free entrance into the presence of our Lord. How long will each of us be there if at all? Got me, but I recall Jesus saying, Assuredly, I say to you, you will by no means get out of there till you have paid the last penny. (Mt 5:26) when speaking about the prisoner who was turned over to the judge.
Let me now say I dont want to come off as a purveyor of doom and gloom. There is the Gospel aka the good news. The good news is that Jesus, for our salvation, came down from Heaven as we say in the ancient Creed. The Lord offers us great graces in our walk if we just seek them out and accept them. Fortunately, He has given His Church the ability to dispense His great graces through the Sacraments. It is through them that we receive our daily bread and receive the sure forgiveness for our sins. I see these as lifelines from Jesus. We just have to reach out and He will reach back to pull us in.