If I may add some tips based on experience.
When I started playing in AWS I was blown away by these huge airlines and found it impossible to be this big. Some destroyed me by attacking me and some beat me "nicely". Whenever I came up against an aggressive player I was destroyed. So I read the forums and tried and tried and soon learned the tricks. Slots, bases, frequency, fuel effeciency! and right plane. It took me a long time.
I started basing in medium sized airports with less competition. Maybe staying away from big European airports as they can be a huge pain in the ass. Try different cities and planes until you find your rhythm and know which planes to get in which situations and how to beat the slot game. My first big airline was in Karachi so it's worth a look. Also Islamabad, Lahore, Jeddah, Riyadh (when it opens), the Middle East is pretty interesting. I haven't tried any but Saudi Arabia but the other looks interesting. I even played in a GW where one of the largest airline was based in Almaty (if I remember correctly) As Sanabas says; basing is very important. It took me over 2 years of gameplay before I've managed to do OK at a Top 10 airport.
Join an alliance later on. You learn so much from it. The forums are great place for info.
There will always be huge players and some will play aggressively and some less but for me it is part of the fun and the satisfaction you get when you can play against/with them and do OK is great.