Just gonna say, before I start, this is mainly for beginners and not those patrons or millionaires out there.

A couple key thing you HAVE to know if you want to make flux is that, "Patience is key" and "You must spend money to gain money" and finally, "There is no easy way".

1. Bombs
In my opinion, bombs are the best way to make money if you are just starting out. Why? Everyone needs them, mostly used to mine ores or to break into dungeons. But.. do you think the rich people out there would actually use their time to actually go and mine it themselves? Of course not. Also, bombs are also easy to make, 10 shapestone and 1 primordial flame. Normally there won't be much profit but you have to wait for the double ore day. Bomb prices go up the day before and ore prices drop during the day. If you want, you could also mine for more profit. I usually get 150k or 200k doing this. Right now(12/26) is a bittersweet time for me because of bonus week. Dub ores for 3 weeks, low prices(really low) but low bomb prices as well, so a good time to stock up.

2. Stellar flipping
Go to /join trade and just keep it open while looking for some good deals. It doesn't have to be stellars but those are the main focus there. You could find deals pretty easily(mostly those gold names that batch sells), buy the good ones and sell them for 5k higher or so, You'll find out what is considered good deals and bad deals later.
You gotta be patient for this to work though, you might have to wait for a couple hours to find a buyer.

3. Shadow tower
If you have extra keys, shadow tower is a pretty good spot to get flux, especially during double shard day. You get shadow shards from killing mini bosses, which could turn into shadow cache and more shadow cache from opening the chest at the end. Each one could sell for about 300 ish and is a pretty nice flow of flux. Grinding shadow tower also gives you a badge so 2 birds with 1 stone.
Also, the titan souls you get also help you out a lot since 3 makes a titan chest and they contain 1.5kf, 2.5kf. 5kf, and 10kf depending on your luck. If you want a stable way, sell them in market. I get about 50k weekly from this(With shadow cache and stuff).

4.Adventure Chest
Unless you have godly luck, selling the adventure chest you get is the best use for them. the MINIMUM you should sell them for is 750f(unless its really common) and some could go up to 1,5k.

5. Dragons
join dragon chat and keep an eye out for dragons that you could go to. It's not that quick but it's a good way to start out. 2kf for u9, 1k6 for u8.

General Tips
1. Marketplace flipping
You could buy the HUGE deal that some people have and resell it at a higher rate but in smaller packages. You need a lot of flux though.

2. If you see people wanting to sell something like ores and materials, lowball the **** out of them. They need the flux otherwise they would be putting it into marketplace.

3. Lowball the **** out of people/compromise
If you see someone asking for offers in trade chat. Just say a price that is a little bit lower than what you would pay for it, but not too low. If they accept, great! If not, just ask how much they are looking for and ask if a price in the middle is too little. 90% of the time they'll probably agree.
Ex: Stellar Face 1*
You say 20k, he says 30k, and settle on 25k.

4. Have emergency money
This is really important. You would spend too much money and you see a great deal but you can't get it because you are broke. Keep some flux in a chest or be like me and stock up on valuable things that are easy to sell(Heart of darkness in my case).

If you are selling, make it a little bit more expensive, only a couple thousand(2 or 3) so just in case someone try to lowball you ,just take away the amount you added.

There's a lot of sellable things that you piled up over time, Just look through your inventory and you'll probably get a couple thousand flux(Enchanted wood, bones, salvage etc). Having a tome helps a lot too. Personally, I use the cybernetic tome because it gives 15 salvage which could go for 20 each(300 f).

Comment what you think if theres something wrong or to add on.
Good luck being rich and if I helped you, I take donations *wink wink*