Well, First you need to purchase an aquarium testing kit to keep track of
ammonia and
nitrite and
nitrate levels. Always buy a liquid
test kit, as they are more accurate then strips. Then best around is the
API freshwater test kit, it has all the tests you'll need and lasts quite a while.
Once your levels show no ammonia or nitrites and about 5 nitrate then you are ready to add fish.
60 liters is about 15 gallons. that is not enought room for an angel, and bettas cant be kept in community tank. A Dwarf gourami would normally be a great choice, but there is a virus going around right now that is lethal so a dwarf gourami wouldnt be a good purchace right now unless you have found a local breeder.
both zebra danios and neons need schools and there isnt really enough room in a 15 gall for both. If I were you I would choose one and have a 5-8 fish school of that.
For algae eaters I would recommend ottos as they are fun to watch and also eat amazing amounts of algae. they are also a schooling fish, but I think that they can be happy in a group of 3. These you should add last, as they are more sensitive to water quality, and you should have a decent amount of algae for them to eat. Their diet will also need suplimented with some cucumber or zuchini after they eat all the algae.
And...
WELCOME TO FISHLORE!!!