Hm...if you just started, I would consider doing some Snarbolax runs. They give a fair amount of crowns for starting players, plus you get some tokens that can get you some nice 2* gear for getting yourself to T2. You can tell if there's a boss gate if you look through the second half of a tier in the gate screen(The screen that asks you if you want to make a group or join a group.) and see a skull on it. Snarbolax Lair should be a green skull.

Arenas are also a good way in making crowns too.

Also, try not to rev yourself too often. Sometimes its better just to give up, save your energy and do it again some other time.(I do admit, there are exceptions...such as a boss being close to dead or you're close to the elevator.) Infact, if you're in a group, if you die, don't spend your energy to rev yourself just yet. A group member can rev you by giving half of their health to you.(Be sure you try to help rev them too. Only when appropriate though...) In groups, only spend energy if everyone is dead.(Make sure if you're the only one doing it, no need for two or more players energy reving themselves.)

And from personal experience, I find ally mecha knights crappy. They end up pushing enemies towards you, and they have a chance of giving you shock when they're near you. So...I wouldn't bother with them. :P

If you aren't a serious player (like paying money, playing all the time) I recommend the Recipes/Crafting route unless you're willing to wrestle around in the Auction House.
Ally Mecha Knights are robotic knights that fight for/with you. Some knights don't like them because the robots are robotic dumb and malfunction all the time (they electrocute themselves and anything touching them every now and then).

Do not craft 2* star items yourself. You can usually get it MUCH cheaper per energy unit used on Auction House. Just be sure to buy the cheapest one.

Find out what you want to be early on in the game. This saves a lot of energy later. There's four classes, usually. Swordsman, Gunslinger, Bomber, Hybrid.

But if you're smart and awesome (Like me. :D) Then you'll find this all out by yourself with the occasional school lunch period spent on reading the wiki.

I haven't decided on a class for myself yet so I'm not really the kind of knight to ask for recommendations. Each "class" has it's advantages and disadvantages. Personally, I think a "Hybrid" is best if you go solo (like me). If you go as a team/party, it mostly depends on the team members.

To go on a Boss run, just look at the Gate Maps before you take the initial elevator. From there you can scroll down and see if a Boss Lair is down the road.