Ehh.. alot of things. Painful to think of actually, know that starting a year later in cryptocurrency would be a huge huge deal in terms of possible gains.

• Don't base your opinions on reddit,bitcointalk,facebook posts. Research everything.
• Don't be lazy and read the fookin whitepaper.
• Don't be too impatient and use market trades. Wait the prices out a bit.
• DONT GO ALL IN ON ONE CRYPTOCURRENCY

Those are just some. Thinking of all my mistakes is pretty much like slapping myself in the face. Well atleast I've learned from them already.   *maybe*

I think about this sometimes. Here is the thing. I had an opportunity to buy 5.000 bitcoins  for 0.01 USD each, so that would cost me only 50 USD back then. Me and my friend discussed about bitcoins then and we were "too smart" and realized all the potential problems and stuff bitcoin will have to deal with like scalability issues and few others. So we were so smart and decided it won't work and I simply decided not to spend my money on it. From that point further I completely stopped reading forums and articles about bitcoin, simply forgot it. Until few years later I spotted news on the radio that bitcoin reached 1000 USD...

So yeah I still joke about this how I missed great opportunity to be a millionaire today. So my advice to past me would be of course buy those bitcoins at that moment. But the second advice would be more important. Dont stop reading forum posts, dont stop watching how project evolves and put more energy and effort in understanding the tech behind it, dont judge too fast...

First advice would make me buy bitcoins at almost best price possible. The second one would probably help me not to sell them when they reached 1 USD LOL ... Bcause that was my initial plan before i changed my mind alltogether... To sell them at 1 USD if somehow they ever reach that point (my words exactly, from past)

Just my 2 cents

Aside from buy "x" coin, i wish i could advice "past me" not to invest in ponzi game, do more research about bitcoin/blockchain and never trust centralized wallet.

My advice to you would be "Daniel-san, never keep your money on BitCoin exchange, always put it all back in the wallets".. Because of mtgox, btc-e and many others who went down and destroyed peoples finances.