The Harlequen Rasboras would be great. I had a small school or about 6 that I bought at Walmart. They did very well with my 1 angelfish. I think that they are the hardiest tetras that you can buy. The coloring is very nice with the orange and the black triangle. If you do not go with those I like the Glow Light tetras also. I find that the neon tetras are sensitive to tanks and I bought 12 at Petco when they had 5 for $5 or $1 each only 7 survived out of the 12. I had no problems with the Harlequen Rasboras with no deaths. Get a school of 6 for your size tank. The Black light tetras are nice also. Sometimes Petco has a sale on those for 5 for $5 or $1 each.
I have a black background in all my tanks and the colors look very nice with the green live plants instead of a picture background. I also have sand instead of gravel in all my tanks.
I have pool filter sand. You can get this at a pool supply store for about $12 for a 50lb bag. It's a courser sand use 1/2 and sell the other half on craigslist. It takes awhile to clean in a 5 gal. bucket but is worth the look and time over gravel. Hear's a picture of one of my tanks with the pool filter sand. Easy to clean as I rub my hands thu small sections of it when it gets algae on it and it comes clean. Pool filter sand also it a beige coloring mixed with other small grains of other colors so poop and stuff does not show up and all the stuff settles on the top of the sand and all you have to do is use a net to get it all to clean the top every now and them.
If your tank is cycled then you only have to do 20-25% water change once a week. I do all mine on Sunday's. I also only feed my fish once a day and skip one day of feeding on Wednesday to keep the water good. I have 5 tiny angels smaller then a dime size, til they get bigger then I will keep a few of them and rehome the others, 7 neon tetras, 1 long finned bushy nosed pleco, 3 Amano shrimps and 3 Black Swordtail
babies, and 2 female Blue tiger endlers and 1 cory catfish in a 30 gal. Bow front live planted tank.