Well IMO I think it is impossible to earn 1 BTC per day. Well you can earn at least 0.01 per day in trading thats the fastest way to earn bitcoins. Try it man you won't regret it.
Under that idea, it is possible to scale up to earning 1 BTC and more per day!
Also, what is recommended for trading (what is best to buy and sell)?
Altcoin trading is also considerably risky and there are other costs involved!
Nobody would tell you what to buy and sell because it would affect their bottom line. They might as well hand you free money instead, as that's what they'd be doing.
A somewhat safe (compared to trading, but still risky) way to earn is by investing in a bankroll. Like
http://moneypot.com -- it hosts many different sites that all utilize the same core BR. When players lose money, you gain. When they win, you lose. But the general idea is that because of house edge, you will, over time, gain. That said, there will be swings up and down as time goes on.
If you aim to get 1btc a day, you must have at least 10btc to start with. I live in that principle to have at least 10 chances of getting my goal amount.
If I want 1btc, I should have 10 sessions or chances to get that 1btc and chances are, I will get my goal on that day.
What I am talking here betting to earn bitcoins. I tried and proved it to myself that if I want to have 100k satoshis, I should have 1 million satoshis to start with and play 10 sessions to get and raech my goal of 100k satoshis.