315 MHz Reciever/Transmitter Raspberry Pi
I have a hunch that your choice of receiver may be causing problems. The type of receiver you chose is the simplest type that can be ordered. Super-regenerative receivers work but are susceptible to noise and interference. Good quality receivers will have a specialized RF frontend that will convert to clean serial output. 

From the product notes of another Super-regenerative receiver similar product:


  Note: These modules are indiscriminate and will receive a fair amount of noise. Both the transmitter and receiver work at common frequencies and don’t have IDs. Therefore, a method of filtering this noise and pairing transmitter and receiver will be necessary. The example code below shows such an example for basic operation. Please refer to the example code and links below for ways to accomplish a robust wireless data link.


With all that said, I briefly looked at the 433Utils mentioned in a few of the comments and it doesn't seem to have any specialized filtering on the input. This could lead to lots of unexpected behavior (especially if there are other devices on the same frequency).

First if you have access to an oscilloscope, I'd inspect the output of the receiver and make sure you have clean transitions between logic high and logic low. If you don't you might need to get a different receiver or get one with an appropriate demodulator (I can try and explain if this becomes an issue).

If not, I'd try and follow the instructions for the same type of receiver and see if you can get it to work at least receiving serial data.

In terms of eventually transmitting to the outlets, once you have your transmitter/receiver working, it will as easy as following the guide mentioned in the comments.