Hi guy,
this is my first post, and i am no pro-investor or something.
But i think i can partially answer your question:

About the "heavy" drop: from what i have seen it is a common thing to happen, that after the first hype for a coin is over,
there is a pricedrop. Nothing to worry about. You will see it fallback more often than only this one time.

I have compared Cardano a lot with other coins,
and there a much signs for solid coin, as the whole setup behind the coin is already outstanding compared to other coins.
Not implying that academics automatically mean more Quality, but the team behind Cardano is pretty big and backed by
Scientists and academic Researchers. Also the founder, Charles Hoskinson was CEO at Ethereum for some time.

Cardano is probably no moon coin in terms that you will see it rise up to 100$ within a year...
It's supply is pretty big, so even if people buy in it will take some time for the price to significantly rise.
But the technique behind is extremly solid and future orientated, so Cardano is defo or atleast some good pick
for long or medium term...

And to get back to your initial question, asking about when's the right time to buy in,-
i can asure you this is now! How should i as a crypto newb know? It's simple; this coin
has entered coinmarketcap with a huge market cap, ranking nearly in the top10 already and one coin is at 2,6 cents only right now,
so time couldn't be better to grab some, as you can already buy a few thousand with only a hundred bucks.
Then wait 1 or 2 years, i am sure this will bring in some good money.

I hope this was of help.

Cheers, Haxel0rd.