I don't have gymnastic rings, what other alternatives do I have?

If you have a portable pull up bar that goes between the door, you can set it low and do inverted rows with it. There can also be places to do inverted rows anywhere in the house: under stairways or behind a table (grip the edge). 

All rows can also be replaced with a dumbbell, a kettlebell or even a big water bottle. The weight should be relatively light and easy to control.

Dumbbell row: take a bent over position and pull the weight next to your body while keeping the hips and core stable. 

Rear delt row: as seen in the picture above. Otherwise the same except you pull more horizontally to the side similar to the bulgarian row. Can be done with one or two weights.

Facepull row: pull close to your head as seen in the picture below. Can be done with one or two dumbbells. A big water pull is very good for this exercise as well. You can lean against a wall for added stability.

You can also do bodyweight air rows with zero equipment. It may look easy but it's very effective when done right. The exercise looks like this:

Similar to other rows, you keep the hips and core stable. Pull your shoulder blades and arms behind with control, hold it there and lower with control. Bulgarian rows and facepulls can also be replaced with this exercise with small modifications (with the facepull you pull next to your head).

Also, gymnastic rings can be worth the investment. They are an excellent tool and can be as inexpensive as $30 USD. Most fitness stores should have them.