Thanks folks! I ordered this:

KRYPTONITE KRYPTO SERIES 2 MINI U L OCK

And a cable, after watching youtube videos and reading sites about how to properly secure a bike.

Later on I will get something better as I can afford it.

Just so you know, we Americans are thought to be very well off, but some of us, like me, aren't so well off. That said, I've seen horrible poverty, at least I know I will eat...

Back on topic: I chose that lock because it was smaller, as recommended, though I can imagine that even smaller is better, but since I will be going to various places, I can't just count on a small one always working where I can lock up.

I have a question: my bike has a rear suspension. There are two bolts so I wonder if locking inside of the triangle to the rear wheel still applies to me...