It really depends on what you want it for. If you want it to keep the kids out, an inexpensive safe will be fine. If it is to deter theft, it may not work out so well. An experienced thief will either rip it off the floor or cut the cable and take the whole thing with him in a matter of seconds.
Even a dang heavy gun safe can be easily defeated by an experienced crook. I have a pretty decent one, and have it mounted as good as it can be, and I could reduce it to scrap in 10 minutes with a battery powered Sawzall. But at least it would take ten minutes and time is a thief's worst enemy.