PVP only requires crowns.

Elevators for the clockworks (pve) require energy, though. Generally speaking, the energy you spend doing a run will usually be covered by the crowns you make on the run, if you pay attention to what gates/levels you're running. Arenas and graveyards have a large payout (though they're difficult!), for example. :)

Plus, you get 100 Mist Energy every 22 hours in addition to Crystal Energy.

If nothing else, energy is *dirt cheap* if you prefer to buy it, particularly considering you generally get a return in the form of crowns when you use it to go down into the clockworks.

Crowns are the coins you pick up in the Clockworks, and they are a currency in this game. Important to note, however, is that Energy is used for many (often more important and gameplay related) activities as well... Which matters because one form of Energy (Crystal Energy or CE) is tradeable between players, either in regular trades or through the special energy exchange window.
All CE is bought with real money initially (except for prizes during lotteries :P), but players exchange it for crowns so they can buy some things. There is no practical limit to the amount of CE you can have at one time.

When using Energy to perform an action, any remaining Mist Energy (ME) you have is first used, and then the remainder (or all if you have no ME) is deducted from your CE, if you have enough. So if you pay 10 energy to go down a floor when you have 100(full) ME, you will end up with 90 ME; if you go down a floor with 5 ME and 200 CE, you'll end up with 0 ME and 195 CE.
Crafting 3 star items and above (mid to end game) REQUIRES some CE, as the total cost is more than the maximum of your mist.

As stated above, it's possible to make enough crowns through running dungeons to buy back the CE you spent on running it in ME/CE; it's even possible to make a hefty profit. In tier 1, unless you do a couple of arenas, this is currently unlikely to happen at the current CE<->Crown exchange rate, but in tier 2 it is fairly easy, and in tier 3 it's very easy to make back the energy you spent lest you die. My point about the arenas is important, because picking the right gate (a set of sequential dungeons) is needed to maximise your profit, if you care about that. General rule of thumb is that Arena levels and Graveyard levels (random chance at some depths) give you the most crowns. The bosses' dungeon sets are also fairly dependable in profit for their tiers.

Hope this helps. Happy delving!

Personally I don't like playing with a laptop, as mine has no mouse. YMMV.

If you have a mouse, or are some kind of masochist who likes using those stupid pad things that laptops have instead of a mouse, then you should probably be fine - as long as your laptop is up to spec of course.

But it at least has a Geforce graphics card. And I use a USB mouse to aim my guns.

I bet swordies and bombers won't have much trouble with keyboard play though.

It still depends on the model and whether or not it has a standalone graphics card.

You don't need an incredibly powerful computer to play SK. Just find something with a sufficient amount of RAM (I recommend 3 to 4 GB) and a decent microprocessor, something along the lines of a dual core would be fine. I have onboard graphics; ATI Radeon HD 4200 and it plays just fine too.

P.S. Welcome to Spiral Knights! Hope to see you around in the game. My characters are Zennyplus (bomber) and Spookydemi (Handgun user)

My laptop (Macbook Pro, don't worry Window fans, I run Windows on it :D) runs the game fine, but I don't wanna go get a wireless/usb mouse for it. Any good controls for a laptop?