Top 20 is right. Even though the price is low, the float is huge, and that means the market cap it huge too, again, even at a low price. Imagine how easy it would be to enter the top 10, or even top 5. I think there's a good chance that people will realize early on the real value this crypto has and it won't be long.

Whether to buy or not? Well, that depends on your risk tolerance and whether you're looking for a good entry on an investment or a trade (in which case your trading skills come into play as well), and, of course, suitability. Everything trading related at the moment is related to ICO price and theoretical values to the upside and time. The investment picture is more involved as it takes into consideration the fundamentals, in this case being the technology, the people, real use cases, and long term projections. I got lucky (in the first 15 minutes of trading) and started nimbling under 500 SAT with stink bids in well below. Someone sold into the buy stack down to 202 and I got filled, not at 202 (never dreamt it would go so low), and I ended up with an average price of 359 SAT, and I'm happy. But this is very long term for me, as in years.

Chart below with key levels as I see it.