Since you're going to have a desktop version of your game, you should seriously consider Steam Greenlight.
I'm part of a small indie team that managed to get our game through Greenlight and released on Steam and it makes a huge difference. Ten times as many people bought the game from Steam as did from all other retailers combined - both online and physical stores.
Yours wouldn't be the first Construct 2 game to try Greenlight either. Over 30 Construct 2 games have been listed and at least 6 have made it through and are on sale (even if in Early Access). See this collection.
As for price, looking at similar games is a good start, but make sure you don't price it too low, you'll get more people buying when you do a % off sale. Our game was originally listed on Steam at $20 but the vast majority of sales came when the game was discounted (25% to 75% off). If in doubt, find the most similar game from a AAA studio and put your game on for a bit less.
As for advertising, before Steam we had been signed with a publisher who spent a fortune on poorly targeted advertising that got us very few, if any, new players. Seriously, it was so bad it would have been more cost effective to hire someone to run around town for a day shouting "Buy this game!". So it's not about how much you spend, but about getting the right advertising.
Getting people to like, share and tweet about your game on social media, getting games sites to do reviews and putting out newsworthy Press Releases will do more to spread the word about your game than pure advertising. Spending $100 to get your game listed on Steam Greenlight is a worthwhile marketing expense, especially if your game is already released elsewhere, given the exposure you'll get.
Anyway, that's enough from me for now. I posted some info on raising awareness about your game and getting your game through Greenlight in other threads if you're not bored already.
Good luck with your game.