To jump on with Jersey I am going to give you the "No Kidding, Here is your reality" according to Davis... This is all my opinion but I think most the guys on here will agree.
Because you are only 19 you essentially have an extremely limited amount of life experience and beyond formal education life experience and personal networking contacts is what gets you jobs.
That means that you need to get life experience and I know that it sounds hard because without working in the field how do you get it? Well there are a few ways and none of them are fast and even more so none of them are easy, they will require years of hard work, sweat, blood and tears, and I am not trying to sound dramatic or anything, but that is just the way it is. You will find on here there are a lot of guys that have years of hard work and life experience and they are still struggling to get the job they want.
So first off you listed two very different career paths... one being basically in retail "tactical" gear sales and the other one being in the emergency services, i.e. LE or Fire/EMS.
1) Tactical gear field... you may be able to go down to your local tactical gear and goodies store and get a job as a sales clerk because of your customer service experience, but I will tell you two realities; 1) most good tactical stores hire guys that have spent time down range or wearing a badge carrying a gun or otherwise responding within the 911 system because those are the guys that have actual first hand knowledge to give to the potential customers and; 2) Even if you do land a job selling tactical type gear in a retail store that will amount to next to nothing on your resume when trying to get hired for LE/Fire/EMS... they will view it has customer service/retail experience but you will not get any credit because you use to sell cool kit to guys.
2) LE/Fire/EMS/ Public Safety in general... I'm getting the feeling that this is where you want to go with your life and that very good, serving your community/country/fellow citizen is one of the most commendable and rewarding things a person can do with their life. But you need to work to get there. Remember that you will never start out being high speed anything, you will have to start in the dirt and work hard to get up the ladder, it's just the way things work. So if you want to be a cop you first need to be 21 or almost 21. Many agencies will let people that are 20.5 apply because they know that by the time you graduate you will be 21. Fire/EMS will sometimes hire guys under 21 but it is getting extremely rare to see that any more because of insurance reasons.
So what are your options... well find out if there are any volunteer fire departments in your area and if there are go volunteer and become a volunteer firefighter and bust your ass, work harder than any other person and put in more hours than anybody else. Go to your local community college and get your EMT certification and then use your EMT with the fire department and maybe get a part time job with the local ambulance company. Again, work harder than the next guy because it will pay off, it will take a couple years but people will notice. While you are doing this see if the local PD has any volunteer opportunities for guys under 21 and if the do, then do that too, even if it is some lame auxiliary type function and it seemingly sucks, do it! Basically if you do all that, then in two years by the time you are 21 you will have started to accumulate some life experience and during the process you will have made connections and networking contacts and when you go to apply for your first LE job with your local dept. you will be remembered as that kid that worked harder and did more than anybody else.
A word to the wise though, if you do go this path, do not be that overly annoying kid that drives the guys nuts, be the one that works extremely hard, asks appropriate questions, does not talk too much and keeps his head down and does anything anytime he is asked. There is a fine line there.
Again this is just reality according to Davis so take it for what you will. I took a wilderness first responder class when I was 20 and thought it was pretty cool and then I went and joined the fire dept., volunteered my ass off to the point that it was basically a full time job; I put in exceedingly more hours than any of the career guys in both training and actual calls, I became an EMT though the dept., did back country ground based SAR, became a HazMat Tech, worked on the fire and arson investigation team, did fire code inspections and ended up as the lead drill grounds instructor at our fire academy; I did all that for about 5+ years but because of the hours I put in I would equate it to closer to 8 years if I had been doing the "normal" amount of hours. I got paid some money as I was technically paid per/on call with the dept. but I had to work another full time paying job on the side to pay the bills but I knew it would eventually pay off and it did. What I got out of it was some incredible life experience, something I would never trade for anything, but even more so I made a name for myself and to a place where some very influential people with impressive job titles would say very good things about me. I had to sacrifice a lot for it... very little sleep, no drinking (so I would always be available to respond) and limited time for personal life and friends, but it was worth it. Because I decided to put in for a job doing helicopter SAR for DOD contracts and even though I was not directly qualified for it I got it because the right people with the those important job titles I mentioned said some really nice things about me. Now just over 6 years later I am still working for the same outfit, I promoted up and currently work in the gear side of things designing new specialty SAR and some tactical related gear and it is a pretty good gig. I still have further life aspirations, such as a gun and a badge at some point, and I know that when I get to that point I will have a lot of great connections that will help me get there... all because I put in the time and worked for it.
If you are still reading, good job! I did not say all that to be mean or a dick, but to let you know that it takes a lot of work, but if you are willing to put in the time you will get there, but it takes time.