I think one has to be careful in drawing conclusions from bible text that one always looks at the context and not just the literal sense.
In particular, Jesus apparently often used parables to illustrate an underlying concept. He did this because he was talking to simple, mostly illiterate, folk with only a narrow experience of life. Therefore he drew pictures using analogies with matters familiar to these people such as vineyards, cattle, fig trees and so on.
He was not actually, literally, talking about investing/trading, he was talking to his disciples about carrying out his spiritual work on his behalf while he, himself, would be away. But he uses an analogy of earthly wealth being utilised for gain in preference to being just "placed under the mattress" because this is something that everyday people could relate to - and one method of utilising surplus wealth in those days, and it still is, was to place it on loan and gain interest on it.
To stretch this parable so far as to claim it also justifies trading in our sense of the word requires quite a lot of mental strength!
For one thing, the servant is using his master's funds and not his own money.
Also, it is clear the master is referring to the equivalent risk of a bank deposit where a return is relatively certain, albeit modest. (although I doubt if the security of deposits with money-lenders in those times was as secure as banks nowadays!)
So, although the parable refers to investing it is not actually about investing and I really don't think it stretches to speculative trading where the entire sum could be blown away!
I can't help wondering what the master would have replied if the last servant had said, "Master I bet the entire sum on a risky venture. I could have made a thousand times return but instead I lost it all"
Maybe the master may have replied something like, "You should have just buried my money in the ground instead, at least I would still have my capital!"
If we use this parable to justify speculative trading then maybe the phrase, "give to Ceasar what is Ceaser's" can equally be used to justify tax-havens and offshore centres to minimise tax liabilities and reduce government revenues, even within those countries where profits have originally been made - in spite of any ethical or moral considerations?
Oh, and one more thing, if one looks at the same story in Luke 11-27, should we also take literally the command given in v.27 regarding anyone who opposes trading?