FL Studio VST plugins for mixing and mastering are not hard to come across with the exception of 1 mastering plugin being an out of pocket expense. The mastering suite I'm speaking about is a VST called Izotope Ozone 4. M-Audio does have an upgrade to version 5 but version 4 still works wonders, but before I go into detail on how I implement it let me explain my set up.
The first thing I do is find an instrumental either I've created or that has been produced from someone else. Then I create a folder titled whatever the name of the track is. Drop the name of the track into folder and open FL Studio. I drag and drop the beat into the digital canvas then I go to File, Save As, find the directory of the folder that was made, name it, and click Save. Now it's time to set up all the processes for mixing and mastering in a simultaneous environment.
The next thing I do is put the instrumental on its own mixer track and in the FX chain these are the effects I put in order, chain number 1 I drop in a Fruity Parametric EQ 2, chain number 7 I drop Ozone Izotope 4, and on chain number 8 a Fruity Limiter. I leave a gap in the effects to make room for additional VSTs if the mix calls for it fx plugins.
I set up my vocal processes in 2 mixer tracks that work together. In the FX chain of the vocal processes I use 3 plugins. I use a Gate first, a compressor second, and a stereo imager or phazer in the third and in turn reroute it off the master and route it to the other mixer track that works as the recording agent.
Before I start to record I turn the volume down on the beat by about -10 dB give or take. This allows me to have some head room for the mastering process. Now back to the vocal process. On the Gate I set the threshold to about -40 which can vary depending on how you have your interface set up. The attack and release of the Gate I leave alone. On the compressor I set the threshold to -20dB, the ratio to a 2 to 1 ratio, and the gain to about 15dB which can also very depending on your mic and/or interface.
This allows for all real time vocal recording to be balanced with the compressor set up that way. The descriptions I've explained on the set ups are on the concept of borrowing the CPU to alleviate having to purchase any expensive external equipment.