"Motion sensing flood lights outside.

No big bushes in front of windows where someone could hide. Thorned bushes are always good for under windows, if you keep them close enough.

A dog is nice.

If you can't afford an alarm and security cameras, fake cameras and alarm contacts on windows can be a deterrent, hopefully. Better to just get the real thing. Remember any security footage could possibly be obtained and used against you if something goes down. If you do shady things, cameras could be a bad idea.

Dead bolt locks on all exterior doors. Keyed outside and inside if there's windows in or next to the door... but then only take the key out when nobody is home, for fire safety.

If you aren't always home at night, get a few timers for lamps inside.

Pro level:

Get a cheap tv. Like a CRT 13 inch that nobody wants. Put it in a cabinet or wall unit type thing, so you can close the door to hide it when guests come over. Put it on a timer to stay on until very late, and set a light timer in a bedroom to come on when it goes off.

Install vertical blinds on a window across from the tv. Vertical blinds are great, because you can angle them for a very limited view, so the house looks less closed up and more inhabited. Anyway, in this case, angle the blinds so you can clearly see the tv, but nothing else in the room. Set volume so you can just barely hear it outside.

This does two things: the light and sound make it seem like someone could be home. And, a thief may look in, see the old 13 incher and just be like damn this dude's stuff sucks, I'm going somewhere else."