As for the landscape thing. Lots of people shoot landscapes and some absolutely incredible ones. But are there really many people sitting there with their checkbooks out, dying to buy them. To be successful you also have to know/understand that what you create, needs to have a market.
That's the number one lesson to be learned in photography. Does this incredible street shot, landscape, slice of life picture, have a market. And does this incredibly cute picture I took of kid, can I duplicate that every other day with hundreds of other kids.
And if the answer is yes, can I market it and make real money off it.