These are a fantastic choice of aquatic live interest, but, it is for advanced and dedicated aquarists only.
There is no easy way around an octopus.
Your best best is to do a google for octopus pets or even octopets, from there search out octopus forums.
Armed with these sites, you will find the right type, and no a blue ring is not a real option nor is a cuttlefish or a nautelus. You will find the proper setup requirements, food types, etc.
Some of the most important items are not usually referred to but will tell the tale...O2 is a must. There must be a very high exchange of O2 into the watertable. A high quality filtration with consideration of the ink toxcitity, excess food particulates, and wastes. As with most predatory species, they make a fairly large mess...which draws in more animals which the octopus eats...etc etc etc. The octopi circle of life.
You can keep fish with them, but, again there are special points that need to be made. Keep them happy, toys and attention, and well fed...theyt prefer hard shelled mollusks (clams, crabs, shrimp) over fish. A hunger octo will eat whatever it can catch.
Good luck. You can email me for exact details and websites if you like. peanutbutterjellyfish at yahoo.com
Ray