I believe this parable is speaking of both personal salvation, and spreading the gospel. It is very similar to the parable of the sower.
Matt 25:14 For the kingdom of heaven is as a man travelling into a far country, who called his own servants, and delivered unto them his goods.
The man is Jesus. The far country is when he rises from the dead and ascends to heaven, he will return some day. His "goods" is the word of God, but especially the gospel.
15 And unto one he gave five talents, to another two, and to another one; to every man according to his several ability; and straightway took his journey.
Note that the Lord already knew each man's ability. This is foreknowledge. He gave to each servant according to how receptive he was to the word of God (revelation, power to witness...).
16 Then he that had received the five talents went and traded with the same, and made them other five talents.
This is a man of great faith, he goes out and preaches the gospel and wins many to Christ.
17 And likewise he that had received two, he also gained other two.
This man also has faith, goes out and wins people to Christ.
18 But he that had received one went and digged in the earth, and hid his lord's money.
This man has no faith, he does nothing with the gospel. He even hid it from himself.
19 After a long time the lord of those servants cometh, and reckoneth with them.
The Lord returns as he promised. Now there is a judgment of those who were entrusted with the gospel.
20 And so he that had received five talents came and brought other five talents, saying, Lord, thou deliveredst unto me five talents: behold, I have gained beside them five talents more.
21 His lord said unto him, Well done, thou good and faithful servant: thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy lord.
This is the man of great faith who believed God's word and preached the gospel. He won many to Christ and will be rewarded. He will rule over many during the millennial kingdom.
22 He also that had received two talents came and said, Lord, thou deliveredst unto me two talents: behold, I have gained two other talents beside them.
23 His lord said unto him, Well done, good and faithful servant; thou hast been faithful over a few things, I will make thee ruler over many things: enter thou into the joy of thy lord.
This man also believed and preached the gospel. He will also be rewarded and rule over many.
24 Then he which had received the one talent came and said, Lord, I knew thee that thou art an hard man, reaping where thou hast not sown, and gathering where thou hast not strawed:
25 And I was afraid, and went and hid thy talent in the earth: lo, there thou hast that is thine.
This man did not think well of God, he thought God hard and unjust. He did not believe. He hid the gospel, not just from the world, but from himself as well.
26 His lord answered and said unto him, Thou wicked and slothful servant, thou knewest that I reap where I sowed not, and gather where I have not strawed:
27 Thou oughtest therefore to have put my money to the exchangers, and then at my coming I should have received mine own with usury.
This man has no excuse, he knew of God (Rom 1). He should have at least believed the gospel himself and been saved.
28 Take therefore the talent from him, and give it unto him which hath ten talents.
To those who receive and believe the word of God, more revelation/power/rewards will be given.
29 For unto every one that hath shall be given, and he shall have abundance: but from him that hath not shall be taken away even that which he hath.
Again, to those who believe, more will be revealed and rewarded. To those who believe not, even that which was given them shall be taken away. They shall be blinded, because they loved not the truth.
30 And cast ye the unprofitable servant into outer darkness: there shall be weeping and gnashing of teeth.
The evil servant who did not believe will be cast in the lake of fire.