As said a good compressor helps in just about every bass playing situation, so not a bad idea to invest in one.
I now use a Zoom MS-60B, so as a multi-stomp it's main function for me is a tuner, but the compressers in it, yes compressors as it has more than one, are great for the price and a nice Introduction to the world of compressors.
As for evening out your tone and attack, i differ from the usual advice on work to get both fingers sounding the same, work on the attack, not the tone, do not sweat it to much on making them sound the same, work on making the attack (volume) even and the rest will fall in place....fingers are supposed to sound slightly different, if the did not then it is no better than a programmed or sequenced bass, and all bass players would sound the same, so what you embrace is an even attack and then a syncopated attack within the nuances of your plucking...that is your "voice", your sound, your style that is what will define you...regardless of bass hour style will be recognised by how you play not so much how you sound.
With that in mind practice muted notes, get your muted notes sounding even without the distraction of tone, if you get them souding even doing this then the rest will fall in place easier when you play for real.