At local big box stores you can purchase a commercial rain barrel that is equipped to connect to your downspout and contains a drain and a screen and everything needed. On this page I show you how I managed to create the same thing for significantly less. At the store the commercial rain barrel can be priced at 80$ or more. I will keep a running total of how much I spend to see how it compares.

First I started with an 8 litre food grade container that I got for free from my cafeteria. I realize this may not be a true cost comparison as I was able to get this component for free, but if you go to restaurants or cafeterias, you should be able to find an equivalent.
I then cut holes through the top as in the following photos.
And so I ended up with this as the top.
I cut off the bottom part of the container - the idea is that since this container has an over lap, I will use the overlap to rest on the top of the barrel, and cut an opening into the barrel top that matches the smaller perimeter of the top of this container.
Here is a different angle to show you the overhang of the top part of the container that will be used to prevent this part from falling into the barrel.
Next I cut a section of fiber-glass window screen that I had on hand. Again this is an item that since I had it on hand the cost is zero, but buying this new would probably only cost maybe 5$.
I held the screen over the lid but into the container and then pushed the lid down. From the inside I was also able to pull the screen to make it more taut. Not seen in this photo, I cut away some of the excess screen visible on the inside. The plus sign of plastic lid that remains was left there because I found in the commercial design that they had support in case some heavy object struck the screen. In this way the screen will not be pushed out. The other purpose of the screen, of course, is to prevent mosquite reproduction.
The next part was to modify the top of a barrel to accept this screen opening. At this point going forward the related costs are the same no matter if you are creating a starter barrel, or if you are daisy chaining barrels, so further costs are not tabulated. In the photo present the shape is slightly odd, this is because after cutting the initial hole, one of the corners couldn't be pushed in so the hole shape had to be adjusted. If I were to do this project again, I would make the lip of the screen piece longer so that it would protrude further into the barrel providing more stability.
Here is a photo of the back of my garage where I will be placing the barrels, notice the down spout from the gutter.
With a hack-saw to cut away the outer three sides of the down spout, and a tin-snip cutter to cut the side of the downspout that is against the wall of the garage, the bottom section of down spout was removed and the flexible down spout adapter was put in place. This flexible down spout adapter is meant to blend with your lawn which is why it is green - too bad they didn't have a white one. Note that there remains a metal clip near the bottom of the photo - I removed this before installing the barrels.
Here are the barrels in place. I daisy-chained them in exactly the same way as is described in the Daisy Chain page on this website.
Here is a closeup of the overflow hose. There is one inch tubing that connects the barrels to each other at the base, and a small section of one inch tubing that feeds a 1 - 1/2" adapter. I had about eight feet of 1/2" tubing that was left over from my SWC's last year that I used as the overflow tube.