I posted this in Altcoin discussion but no one answered and the post got moved to 2nd or 3rd page... So I'm reposting this here as I really need the answers because I'm about to buy more coins
You can make another post in a thread to bump your thread up to the front page. The general rule is that if you created a thread you're allowed one bump post per day. All you have to do is write "bump", but adding new info or asking a new question may help generate more response.
1) First question. Am I correct thinking that BUY/SELL is to buy BTC straight from the exchange at a predefined price, and TRADE is to buy from other people at prices set by those people?
You are not correct.
To Buy/Sell is to buy or sell BTC with another currency. The price for which you buy or sell is usually the "market price", that is whatever the price is at the time you click "buy" or "sell". Some exchanges will allow you to set a "limit price", which means you choose which price to buy or sell and if the market price reaches your limit price the buy or sale will be initiated.
To Trade is the same thing, without the specifics of which side of the market you're on. Or you can use it as a verb, "I'm trading my cryptocurrency". It's just exchanging one thing for another, in this case USD for BTC or BTC for ETN.
2) I believe it is possible to play around with the above options for better rate? Do you think I overpaid? I really need help with this one guys.
Sure it is! You can set a limit price, thereby ensuring that you won't pay too much or sell for too little. There is only one downside, you're not guaranteed the market will head your direction, the transaction may never hit.
Your new to this, the swings are wild. The price of bitcoin can swing 15% in one direction and then another in the same day. You'll get used to it. You'll also learn that it might be a good idea to keep some money on the sidelines to buy in a lower price when the next dip occurs.
3) Is there a difference between buying with USD and GBP? The deposit price was the same for both at 3% or 3.5% + 20p or 25c.
Yes, you're using a different currency to buy your bitcoin. If you have the same amount of money to buy with ($100 or the equivalent in GBP), you should see which currency can buy you the most bitcoin. Usually it will be the same, but at times you might find anomalies in the price. These are called arbitrage opportunities, where you might be able to buy more with USD than with GBP, considering the same investment amount.
Now a question for you...
Why didn't you buy your 1000 ETN directly through Cryptopia using USD, GBP, or whatever fiat currency you're using? You would have saved all the fees by buying the BTC and then sending it to Cryptopia and then trading it for ETN.