Her laning phase now is a bit rough she is a lot weaker so starting with potions is very good. If you are against ranged champions I would suggest wait out and farm with Q till level 2 to get your shroud. Once you get shroud wait for the ranged champ to use their cc spell or any spell really. Once this happens Shroud and Q them, walk back in and auto then Q then auto. That is a basic combo which can get them to half health easily. Once you get level 3 before them and see they wasted the spells go in with e then shroud and do the q combo you will probably get a kill with ignite as well. Also don't be afraid of the jungler use your combos on the jungler when the mid laner is far away. Easy kill, the jungler is basically your second way to farm kills.

Akali's nerfs made her Mid and late game fairly weak because the shroud isn't as good.
As akali in the mid game you should have won your lane. If you did look for roams try helping out top and bot. You can also pressure jungle as well. To go in always use your Shuriken Flip then Shroud. You can also Flip then shroud do the basic q combo and use ultimate for the finishing move.

If you are not fed at all then you will not be able to do anything late game. As akali now you are only focused on killing the squishy back line and nothing else. ONLY ENGAGE on tanks when you have your team. Only way you can get kills is by Ksing with your ultimate....Just how life works. Remember to always engage with E because its the safest especially if your new. Engaging with R is mostly for helping your team get kills but you can use the second R to steal it... Good money ;D

Tips for Akali, I suggest being very aggressive because you always want to snowball with Mejais. Don't be afraid when the jungle comes, depending on which jungler it is they are basically free kills if they over extend without the laner. Akali is fairly good at 1v2s in the early game so target the squishy enemy when your in a pickle and can't get back to your tower. I usually don't go mobility boots but if your very good then go help out your team with mobility boots.