To be honest, you'll be a wild card candidate because it'll depend on the adcom's own personal biases and value judgments of what you do (i.e. will they respect what you do, or will they only see you as an "organized ticket scalper"). Harsh, yes - but that's the truth. All you can do practically speaking is to do the best you can on the application in conveying your strengths and experiences -- and how such skills will be transferrable and an asset to your future finance career - but you won't be able to change an adcom's personal biases - they will either respect what you do, or they won't. On top of that, the fact that you did a law degree but haven't practiced is a "strike two" -- a perceived lack of focus (because you're now applying for yet another graduate degree - and the adcom has to take at face value that this time, you really want to follow through on a career that is related to your graduate education.
And on top of that, it looks like you've had little group/team/leadership experience as your work experience to date has been mostly solo (and no, signing up for volunteer work right now is window dressing - it's better than nothing, but it's not really going to help a whole lot if you're doing it for less than 2 years). So that's strike three.
And strike four is that b-schools do value structured group experience moreso than entrepreneurial experience - in spite of all the hoopla about "entrepreneurship", the MBA is still primarily geared towards graduates who are going on into more traditional corporate environments (including yes, working in finance). Given your lack of big company experience, b-schools will be concerned about your ability to be effective in a more structured group environment - whether it's the group work that is the foundation of the MBA program, or post-MBA in a role where you're working in a company where you're not the main boss. To be blunt, in the absence of substantive corporate experience, they are worried that you'll be a loose cannon - that you'll be difficult to work with in school, that you'll have a harder time finding a job, and that if you have a job -- you'll have a hard time working for someone else. Also, the fact that you mentioned working in a traditional environment to be a "step down" from your "high risk, high pressure" environment suggests that you are underestimating the value of that experience, and overestimating the value of your own experience. To be blunt, adcoms will have concerns that you have the ability to work *with* people in a team, which is something essential to the b-school academic environment as well as virtually every post-MBA job out there.
I don't mean to steamroll you here, but you have an uphill climb. Not an insurmountable one, but you have a lot going against you. What that means is this -- apply to your target schools, but have some realistic expectations. Have a plan B that does not involve an MBA (i.e. trying to get that sales/trading job without an MBA - it may mean that you may not get your ideal position at a large bank, but will likely be for a smaller player - and then using that experience to work your way up).
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