QUESTION: About Trading Cards, Trading Card Packs, Level Up

Some people sell some cheap bundled games for trading cards, you can try there, just don't sell them on the market or you will lose a lot on taxes. Doing badges is just for exp, you don't get anything but losses from it (imagine using seven 0,05$ cards for a badge only to get a 0,03$ emoticon and background).
For the cards pack...you can find foil from them so you can gain more from it, but it's random.

A lot of players wish to craft the non-marketable sets. If you are wanting to trade them away for marketable cards then advertise on the particular game's trade forum (a sub-forum of the game discussion forum). You can ask for marketable cards in return for your boosters and cards. Some will ask for other marketable items such as keys for TF2 that can be easily sold on the market. Others will accept gems for the cards.
You can use this website https://www.steamtradematcher.com/ to give yourself an idea of the worth of your non-marketable cards. The worth is subjective I guess, you are free to put any price you want on your cards.
Boosters can sometimes get more - there is a chance for a foil in there. Most will want to treat a booster as three individual cards though. The chance of getting a foil is very low.

If you don't want to spend too much energy for too little gain, just sell all of them using Steam Economy Enchanter (or alternative if there is one).

I might want to sell them all and gain some Money from it. Or would it be more of value for me to get badges, Level up and gain emoticons and backgrounds I could sell on the market?

It really depends what you're after.
If you want to make the most money, I'm pretty sure it's best to sell the cards or the booster packs rather than the produce of their crafting: they have more value because they allow you to get both XP and the craftable items.
If you want to try your luck, well then you could craft the badges and hope to get a rare item. That could make more money than the cards... but only if you're lucky (on average, I'd say you should expect less money from craftables than from cards).
Because of Steam's transaction fees, selling booster packs is on average more profitable than selling the resulting cards. Again, if you want to play "feeling lucky", you could open booster packs and pray for rare cards (but again, on average, you should expect less money from cards than from booster packs).

Personally, I find it too time-consuming to trade cards... What I do is I sit on them, I just set for sale my most valuable foil cards and some of my booster packs (those for which either I already have the level 5 badge or those that are really noticeably valuable). And from time to time I use steamtradematcher to try and complete some sets. If you want to get rid of some cards and exchange them for complete, ready to craft sets, there is also steamlvlup which can be used for that (I haven't used them in a while, they seem to be still running fine).

But I have an interest in leveling up (a bit), if only for the friend slots and the badges, and because I find Steam's fees quite of a rip-off on 0.03$/€ cards (fees are 0.02$/€ on those...).
If all you want is to make the most money (which probably won't be a lot anyway), without spending hours negotiating on forums, I'd say just sell your items without transforming them (and use steamlvlup to exchange unmarketable cards for marketable ones). Steam Economy Enhancer, which was mentioned above, seems like a nice helper to speed up the process of selling your things (I've never used it myself).

i have a good marketing strategy for selling cards i always sell them 2-4weeks before a sale ,they usually increase in price from those bulk purchases for leveling .
sometimes i sell some cards for 0,20 instead of 0,07Euro
i have a brain filled with math ,so i actually remember all cards with a bit of value and check them .
i probably gain some 3-6Euros more for each sale than i would otherwise while selling those cards .
I would always open 5-7cent boosterpacks .
You usually gain more and maybe get a foil one and hit the jackpot . (except trash cards are only worth 3cent) those boosterpacks you wanna sell .
With 5card badges from trash games or usually 5-7cent boosterpacks you can usually Gain Exp on sales and gain the Extra card and Emote/background and you will get Exp and the money .you would gained by selling those trash cards .
so i always sell only cards with Value or with to many cards .