Market price is only available during trading hours.
If you buy, it is the current sellers' price.
If you sell, it is the current buyers' price.
It has associated risks.
As you say, limit is the price you want.
If it reaches your price, your position in the cue and there is sufficient liquidity, you get a full fill.
If there is insufficient liquidity you may get a partial fill (paying full brokerage).
If you keep the order open long enough, it may eventually fill.
The Broker is not your friend!
And Mr T says:
"Remember your ABC!
Always be cool!!"