Good gambits for beginners vs 1. e4?

Basically just the title

modern scandi is a good choice

1 e4 e5 2 Nf3 Nc6 3 Bb5 f5

I like to play the Scandinavian against 1.e4. I like the Nf6 version (1. e4 d5; 2. exd5 Nf6). It’s not really a gambit, because usually you get the pawn back.  But in its favor is that whatever White started out wanting to play, they don’t get to play it, and now they’re playing your opening instead. I have fun with it.

I'll throw a list of gambits against 1e4

• The fred 1..., f5
• The modern scandinavian 1..., d5 2 exd5, Nf6
• The latvian gambit 1...,e5 2 Nf3,f5
• The elephant gambit 1...,e5 2 Nf3,d5
• The philidor counter gambit 1...,e5 2 Nf3,d6 3 d4,f5
• The rosseau gambit 1...., e5 2 Nf3, Nc6 3 Bc4,f5
• The janisch gambit 1...,e5 2 Nf3, Nc6 3 Bb5, f5
• That gambit in the three knights 1...,e5 2 Nf3, Nc6 3 Nc3,f5
• The petrov defense damiano variation 1...,e5 2 Nf3, Nf6 3Nxe5, Nxe4

There are also some gambits that go after the fried liver like the traxler smd others.

Personally I recommend the modern scandinavian and the latvian, the latvian is unsound and chaotic, very risky only for people who really know tactics but you can cut a lot of theory with it because you get to play this gambit at your second move! as black.

Of course you can play the fred right after e4 but the fred is just trash.

Can you please show, i dont understand

Latvian ganggggg (btw you forgot the stafford which is really fun to play) 

The modern scandinavian 1..., d5 2 exd5, Nf6
The janisch gambit 1...,e5 2 Nf3, Nc6 3 Bb5, f5

Those 2 are OK lines, and they only sometimes result in pawn down positions.. Some of those listed are just not good. I think the engine evaluates the Latvian gambit as about +1.5. I won't play something like that. Are there gambits for black which are really playable?

I always play gambits as white aftee 1.e4 e5, but play Alekhine's as black, 

The engine is going to rate every gambit as losing with perfect play. I can admit that if your oppenent plays well your going to end up a pawn down in the latvian but its really good for taking people off their prep and being able to do it move 2 is pretty good. the rousseau is good but easy to decline and put you in a normal game. The stafford is also easy to decline but if they accept it it just boils down to who knows more theory. The problem with black is that almost no gambits give you intiative and the ones that do arent too good. But with all openings, the best one is the one that works for you depending on what your playstyle is

1.e4 d5 2.exd5 Nf6 It is technically a gambit because white can try to hold on to the pawn. Many beginners will try to do that (and many intermediates as well. I beaten players 1900+ in this opening, the thing is when they are higher rated than me they think they can take the pawn and get away with it because they are better players than me. Usually they don't get away with it). 

If white wants to be a pawn up stockfish gives slight advantage to black. In practice black is much better despite being a pawn down. I mean the fact that stockfish prefers the player that is a pawn down tells you everything you need to know about how dangerous that is to play with white.  

The Marshall Attack
1 e4 e5 2 Nf3 Nc6 3 Bb5 a6 4 Ba4 Nf6 5 O-O Be7 6 Re1 b5 7 Bb3 O-O 8 c3 d5

I know I forgot some gambits, yes the stafford is like almost +2 , the latvian is unsound but I like it not because the engine evaluation but because the chaos it gets on the board (chaos for both players btw) not for everyone s taste. I played the albin counter gambit in a 30+30 lichess game against a guy rated over 2100 and almost won, it was a bishop + pawn vs a lone king but unfortunately it was a draw. 

I still love my classics: the King's Gambit. It's the best gambit against 1. e4, no questions asked.

Below is how white can decline a gambit in the center counter and transpose to the Panov attack. If black plays e6 instead of c6, white can similarly transpose to an exchange French. White can take the pawn either way, in which case black has decent compensation for the pawn, but certainly not an overwhelming attack as black. This is a reasonable gambit line, but white usually does not play c4, and as mentioned can give back the pawn.