osmfilter to extract all admin boundaries as areas and all places as dots

Before importing a huge world osm file with using osm2pgsql, I was recommended to use osmfilter to filter the input file down first. So that an osm file used for import only contains data that I need.

The final goal is to get all admin boundaries as areas, and all places as dots (like cities, villages, suburbs and so on). This data will be used in the following way:

• admin boundaries are used to render a very simple map of a particular country (infographics)
• places are used to put cities (as dots) on that map

That's basically all we need from the data.

We would like to automated populating data, so using osmtools sounds okay.

Тow, if the first stage is to filter down the big OSM file, what's the best configuration to only have data described above and nothing else? So that the final database is of small size and can be queried very fastly.