I will appreciate any card you send me, no matter if it is a free card, a professional or a handmade one. But you can do me a big favour by using a beautiful stamp (or two or even more), commemorative stamps would be great, although many countries have very beautiful "normal" ones, too. Your card will stay in my collection for sure.
If it is not too expensive for you (in Germany it is the same price) it would be awesome if you could include some stamps or a small coin (my sister will be very happy about them) in an envelope.
No idea of what to write?
-send me a short riddle (a mathematical one?)
-teach me something in your language
-tell me something about you and your life
-write some curious facts about the place where the card is from
-give me a local travelling tip from your area
-share an interesting news bit if anything important happened in your country lately.
-tell me about a local festival or tradition from your area
-write about you unusal hobby or collection
-tell me about your favourite book, movie or band
Some ideas of motifs:
landscapes, animals (I prefer dogs), culture, ... whatever
No matter how you decide I am happy about anything you send to me.
Usually I register received postcards the same day.