I would like to buy a rain gage and wondering what to look for and does it matter where I place it, as long as it's not under trees or roof-lines it should be accurate right?

I have our rain gauge attached to the fence line. There are no obstructions there and I get an accurate reading of rain that heads straight downward. But if the wind is blowing, of course it does not catch a lot of those drops. IDK if there is one that does??

I have a nice wrought iron holder that accepts the inexpensive glass tubes about the size of a test tube Found in feed or hardware stores. They tend to crack in freezing weather, not sure why, there is plenty of expansion room. I don't know physics.

Come to think of it, I had one like @Bonehead. The test tube-like vial would sway in the wind, catching the rain I guess? It was pretty. It disappeared along with my sundial one night.

grew legs. that is a bummer. So far I have not had that happen, but who knows, someday it could

My plants seem happy if they get about one inch of water every week.
So I just place empty bowls, jars or pails around the yard.
I can estimate after a rain whether there was an inch of rain.
Right now we are in a heat wave ( for us) and so I need to water them by hose.
The critters who visit my yard appreciate the containers for water.

I hooked one onto my porch railing where I can see it from the kitchen window. Unobstructed overhead, no gutters or roof overflow. It seems quite accurate- for comparison I look at the Weather Underground website- someone only 1/4 mile from me has a weather station including a rain gauge so the info is constantly uploaded onto the website. If I did not have it, at this point I might not buy one as I can get the info off of Weather Underground.

I use the water from the rain gauge to water the plant that sits beneath it. Tomorrow it gets 4" from the container.

This is just a theory, but wouldn't a BIG rain gauge be more accurate than a small one? A big mouth would "average" the rainfall over a larger area and be more representative.

You could also make one more precise (or easier to read to 0.1 inch) by using a very large funnel narrowing down into a narrow tube. Say the funnel mouth was 4"x5" (20 square inches), and the tube had an inside diameter of 0.64" (one square inch tube ID).

One inch of rain would fill the tube to 20" deep, letting you read the actual rainfall to 0.1" or even 0.05". (Or you might run the rain into a jug and weigh the jug to get even more precision.)

Please, no jokes about my "big mouth" expertise!