Previously, here https://steemit.com/eos/@ivrmakers/eos-crowdsale-did-you-participate-step-by-step-guide-part-1 we learned to install metamask. Here is a little overview of the interface..
After clicking on three dots, you click on "view account on etherscan", you will see something like this..
ETHereum works on GAS, which is the fuel, consumed by the network to do the "work". Example, you want the answer of 2+2, it may consume 1 gas & some complex problem like (2+2) * (9/8) may consume 3 or more gas. More complex the situation, more gas it consumes. When performing an ICO or D-app transaction, interface will ask you gas limit & may also show the gas that function would require.
GAS LIMIT: This is the maximum amount of gas YOU ARE WILLING to to spend on this transaction. In above or more complex example, if you set gas limit way less, say 1, transaction may fail by giving OUT OF GAS error & you loose your fees. If you put 100,000 or more than what is written on the contract & the operation consumes less gas, the difference will be returned back to you. (Lowest gas limit is 21000)
Next comes the GWEI i.e. the price you are willing to pay per gas. When performing a transaction, interface will ask you the gas limit & the gwei. More the gwei, faster your transaction executes. Lower gwei may result in delays for hours or days or weeks or maybe that doesn't execute at all.
You can always check the latest gas & gwei info on https://ethgasstation.info/ This is at the time of writing.
Standard lowest gas limit is fixed at 21000, so if you put gwei as 3, your transaction would cost you
(21000 * 3) / 1,000,000,000 == 0.00063 ETH or USD 0.05355 ( 1ETH = USD 850 at the moment) & this transaction may complete in around 22 minutes.
Most miners look for high gwei transactions, but its not always the case. You decide your transaction value. If you want its execution fast, pay higher gwei & if you dont care much, like I did by putting my crypto kitty for sale with gwei 0.1, its already been 2 days & says will still take more than 1 day, but if it executes, I would have paid lowest fees of 0.0000235507 Ether ($0.02).
Hope you enjoyed reading through this long post & learned something.. If you have any queries, leave the comment below, & yes, don't forget to upvote & follow for next updates..