The Apostle Peter taught that faith in Jesus is crucial for salvation:
And there is salvation in no one else, for there is no other name under heaven given among men by which we must be saved. (Acts 4:12)
So that means misguided Buddhists, Hindus, Muslims, and members of any other non-Christian groups cannot find salvation in their religion, no matter how devoted and sincere they are.
But what about Christians who may be confused about some basic Bible teachings? The Bible doesn’t explicitly discuss the issue of doctrinal requirements for salvation. We can use what the apostles taught people before baptism as a guide, although it is not clear what happens to people who may accept most but not all of these teachings.
It is a useful exercise to go through what the apostles preached (to non-Christians) and try to make a list of the main doctrines taught. One attempt at a list is here.
While the Bible is not explicit on doctrinal errors and salvation, it does comment on other barriers to salvation. For example, Jesus warned that there are some people who think they are following him but who will not be saved.
21 “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. 22 On that day many will say to me, ‘Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?’ 23 And then will I declare to them, ‘I never knew you; depart from me, you workers of lawlessness.’ (Matthew 7:21-23)
This passage clearly shows that being a Christian and doing religious work, even sincerely, does not necessarily lead to salvation. Later Jesus warned of people who were religious but would not be part of his Kingdom because they had neglected to look after those in need (see Matthew 25:31-46).
In fact, the only way to be saved is by grace through faith (Ephesians 2:8), although Jesus makes it clear in the passages above that one’s faith is meant to be expressed in works (“doing the will of my Father”).