Ethereum - How to choose GAS limit before transaction?

[howard.ashoul]

Lets say I want to send 5eth. And I will set gas limit to 200 000.

1) During transaction it will burn only 150 000 gas. So it will charge me only 150 000 gas, not 200 000 - from the funds I have in wallet?

2) Since I never know gas needed upfrom, its impossible to empty my ETH wallet? Since I need keep there 200 000 gas (in form of ETH) but I don't know upfront, how much it will charge me? And if it charge me only 150k, I will still have money left in wallet (50 000 GAS in form of ETH). So impossible to get my wallet to 0?

3) If I set some ridiculous limit (1 000 000 000) it will still charge me only 150 000 gas?

4) What is ideal limit for normal money transaction? What is ideal limit for ICO transaction (smart contract)?

[howard.ashoul]

Anybody, please? 

[freebutcaged]

Whatever you pay it will deduct from your balance mate, why would you set crazy limits like 10,000,000? you just need to pay 20,000 for normal

Transactions and 200,000 for ICO token transactions. if you pay more gas it will be deducted from your balance, I just don't know why they call it

Gas while it's the same Eth which will be paid to the miners. maybe some one with more knowledge could correct me if I'm wrong.

[Kriptex]

Whatever you pay it will deduct from your balance mate, why would you set crazy limits like 10,000,000? you just need to pay 20,000 for normal

Transactions and 200,000 for ICO token transactions. if you pay more gas it will be deducted from your balance, I just don't know why they call it

Gas while it's the same Eth which will be paid to the miners. maybe some one with more knowledge could correct me if I'm wrong.

The most detailed about this concept is located here:

https://myetherwallet.groovehq.com/knowledge_base/topics/what-is-gas

I was so confused on this concept while I'm doing ethereum transactions and after I read this source, It became very clear in my mind. Try to read from there. It will absolutely help you.

[howard.ashoul]

Thank you!!!