my advice would be to write about a very niche topic, something that searched quite a bit every month, that doesn't have much competition. No point jumping into a field with high competition. Even though you will have to late on to get the higher paying clicks.
but for now , try and think of something you searched for once and found very few sites with the answer. That's what I do and it works for me:) I have a problem search for an answer and cant find it anywhere solve the problem and wipeee i make a hub about it.