Beginners help please

I know they say that there is no such thing as a stupid question, only a stupid answer but I, going to try.
Amassed a few miles and some tier points over the last couple of years which I thought may get me an upgrade from, say, Econ to PE.
But I'm a little (lot!) confused by all the ticket types etc.
Looking at Las Vegas, I can look for the lowest economy ticket but that doesn't allow me to upgrade. If I look for a qualifying ticket I'm looking at almost double the fare, thus making it cheaper to upgrade from the lowest fare and keep my miles.
So, some questions,
Do I need to look for special offers to use these miles?
Are they worth anything in reality or are tier points the way to go?
What are the benefits of tier points?
What's the best way forward?
I would really appreciate any advice,
Simon
Amassed a few miles and some tier points over the last couple of years which I thought may get me an upgrade from, say, Econ to PE.
But I'm a little (lot!) confused by all the ticket types etc.
Looking at Las Vegas, I can look for the lowest economy ticket but that doesn't allow me to upgrade. If I look for a qualifying ticket I'm looking at almost double the fare, thus making it cheaper to upgrade from the lowest fare and keep my miles.
So, some questions,
Do I need to look for special offers to use these miles?
Are they worth anything in reality or are tier points the way to go?
What are the benefits of tier points?
What's the best way forward?
I would really appreciate any advice,
Simon