My Thoughts On Collecting And Some Advice Would Be Nice

If you are buying key or semi key coins, I would only buy them slabbed. This is due to the high prices of the coins, and I personally would hate to pay a lot of money for a coin and then later find out it had been cleaned and was worth way less.

^ Sounds like a good idea for me. Only American coins interest me though.

There is nothing wrong with your logic as far as it goes.
I'd just like to take it a few steps further.

"I have recently decided to start buying semi and key date coins in different series."
Why? For investment or for your own personal enjoyment?
just carl gave you a definitive answer as to the difference.
Pay attention to his advice.

"I usually buy from a coin shop I trust and I tend to like raw coins. But recently I picked up a few coins from them and it turns out they were cleaned."
OK. Have you spoken to this dealer, explaining your disappointment?
Perhaps a simple, "In the future, only show me raw coins that have not been cleaned." will tell you by way of examination whether or not you might continue to do business with them. Of course, this will require you to learn more and more about detecting cleaned coins.

"After finding out they were cleaned I'm starting to think about abandoning raw coins and get only slabbed coins."
Here, you are going too far in the wrong direction. I just
recently spent in excess of a grand on two, raw nickels.
I am confident that they are just fine. But I also bought another nickel [ from a different dealer ] that, upon closer inspection, has been cleaned. I am out $19 on that one.
Lesson: you will make mistakes, just make them on the cheaper coins. I STILL DO!
[and so do many dealers who have been in the business for years]

"Its more of a way to get the most out my collection."
And there you have it, COMET - you must ask yourself by what
criteria you judge "the best way to get the most." And do not think that you will not change these criteria over time. It is a guarantee that as your needs change your goals will change.

Look, coin collecting is supposed to be fun. And it is.

If I were to actually give you advice I would want to know
just what series of coins are of interest to you. The dollar experts will help you with the Morgans.
Any more details you care to give?

Thanks for the advice. My main collection are Morgan dollars, these I usually don't have a problem with when it comes to detecting cleaned or altered and such. But when it comes to other series sometimes I get confused as I am less knowledgable, so I can't completely blame the dealer. In this case it was Peace dollars.

I'm not looking into making money on coins but I do want to have un-cleaned coins for my collection. I'm pretty sure the dealer would take the coins back if I asked him. But again I would like the keep these for my collection and learn how to spot cleaned Peace dollars using these coins.