I like the OP don't use margin. Long term it will lead to trouble, it may work for a little while but long term the trend is against you. Especially when you have a larger account they will give you 4x margin, this is a great way to loose a lot of money quickly if the market makes a quick turn against your positions. To be clear the market invariably at some point will quickly turn against you!!
In my opinion, and practice, emergency funds should not be used for investments ever, this includes covering the losses from investing. Yes it can feel like you are not maximizing your returns on that amount of money but its job isn't to generate returns, it is your help smooth out the bumps in the road of life for you. In my experience life can punch hard and it never throws just one punch, it is usually a 1,2,3 combo. That emergency fund is merely there to help raise the chances of you standing on your feet after the vicious flurry.
If you want leverage and you are in the US or have a US based brokerage account use options. By using options your all in is basically the cost of the option and this ensures you will not ever lose more than you paid. PLEASE note the previous sentence is predicated on the golden rule of NEVER WRITE an uncovered/naked option, seriously do not do it!!!! I also use the 5% rule, which no one trade is more than 5% of my portfolio so no one trade will destroy me.
