Setting up a 1-node ethereum testnet is not too hard (though it's not especially user-friendly either). I did some work with Ethereum last year, and I ran a 1-node testnet on my laptop when working on code. The node was mining constantly, but it didn't seem to demand too much from the CPU. No excessive fan noise or heat.

Both embark and truffle, two commonly-used frameworks, have modes that exercise the CPU even less, though I found them a bit hit or miss. I'm sure both have improved since, though.

I did a quick test run on the main network as well (which wasn't too expensive - maybe 1ETH). You're definitely better off using a testnet! - the turnaround time is much shorter.

Just download the mist wallet and mine on the test network which is what you should be doing if you are playing with it anyway.

https://github.com/ethereum/mist/releases

You can buy the Ether on an exchange.

I was hoping for a roughly low barrier of entry, rather than try to figure out who will trade USB for ETH, as I have no BTC.

In all honesty, I'm looking at distributed applications as well, which from what I read Ethereum says it does and doesn't do. It's a bit fast and loose from what I read about, about Ethereum's capabilities.

I'll go back to my experimenting with TOR and how it might be possible to make your own distributed applications within the Hidden Services. That's free to use, and as low bar as I can think of. (Add machine, shows up as HS.)

As other posters have mentioned, you can download the Mist client and test things on the testnet.

And you don't have to mine, you can get free testnet ethereum via the wei faucet:

https://zerogox.com/ethereum/wei_faucet

Gas prices to run code on ethereum are fractions of ethereum, so even a small amount will get you pretty far.

While developing, you would do it either on the dev (local, not connected) or testnet. Both these are easily mineable (I have 10k's on both), so there is nothing stopping you to actually playing around and putting together a dapp without having real ETH in your pocket.

No expenses and you can play around all you like. When you want to go live, there is typically only a very small deployment cost.

Relatively inaccessible means of exchange are a persistent weakness of non-domestic currencies.

Hope your experimenting goes well!