I would suggest:
Smiling -- the cheapest and most effective beauty enhancer
(or: "Smile! It's the cheapest and most effective beauty enhancer", or:
"Smile! It's the most inexpensive and most effective aid to beauty")
A smiling face is always beautiful. I have never seen an ugly smiling face. In fact, there is no such thing [as an ugly smiling face]. A smiling face is meant to be beautiful in its own magical way.
Apart from the celestial beauty which a smile gives to us, it has numerous other advantages over the other modern beauty products and cosmetics.
You donít have to go to a shop or the market and spend hard-earned money on a smile. An innocent act of a child or a call from mother or an old friend after a long time can bring a smile to your face (or: "put a smile on your face").
The magic of a smile is instant. Your eyes light up and it brings a charm to your face.
The supply of this makeup is inexhaustible. It can be used anywhere and at any time.
There is an aura of happiness around a smiling face which lights up every being around it. Needless to say, this aura of happiness is far better than the artificial fragrance of modern perfumes and deodorants.
The best feature of this make up is that it is contagious. A smiling face triggers the same effect (perhaps "response") on the faces of other people.
All this (or: "All the above") shows how a smile surpasses all (perhaps "is superior to") the features of modern beauty cosmetics. So donít wait, just smile and avail yourself of the benefits of natureís most effective makeup, i.e. a smile.
That's very good, and you're so right! It is mainly tweaking that I have suggested. Just a couple of points: with the comparison of adjectives, it is either "most cheap" or "cheapest", but you cannot combine "most" with a superlative.
It is "avail oneself of" in this case: to be of use or advantage to.
I think as a matter of style, there is no need to repeat "as an ugly smiling face" in the first paragraph.