About purgatory and mass, these traditional beliefs are generally associated with the Catholic church.
The idea of mass, as conceived by the Catholic church, is not taught in the Bible. Please see these links for more details:
http://www.insearchoftruth.org/articles ... tantiation
http://www.insearchoftruth.org/articles ... #sacrifice
Purgatory is also not taught in the Bible. It has many problems. First, the Bible clearly teaches that after men die they face judgment (Hebrews 9:27).
Furthermore, Jesus describes separate places of habitation following death, paradise and hades, but a great gulf is shown between them (Luke 16:19-31). And, it was impossible to cross from one side to the other (Luke 16:26). There is no temporary state or condition between heaven and hell, whereby one can suffer or struggle sufficiently to finally achieve heaven. It is simply not taught in Scripture.
Furthermore, the idea of purgatory is dependent upon the idea that man may improve his state through his works apart from God, which his contrary to the gospel's justification by faith (Ephesians 2:8-9). Also, it is based upon other traditions not taught in Scripture, like praying for the dead, etc
Since these practices are not taught in Scripture, and since they stand contrary to Scripture in many points, I would encourage you to reject them.
More detail could be given. If you have specific passages or proof-texts, which you would like to study, please let me know.
May God help us to have a sincere love of truth,