Should I learn the Evans Gambit at 700 rating?

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No, learn boring openings like London, Italian, etc. If you want something more vibrant go for the Vienna Gambit.

If you want to, sure why not

It always depends on your definition of "learning". The Evans Gambit can teach you a lot of things about material, initiative and dynamic play. So look at some sample games, try to understand the key moves and play it to get a feeling for the position.

But should you memorize some computer lines? Hell no!

No, don't learn the evan's gambit

The Evans is a great opening to learn how to play with the initiative, and how to play chess in general. So why not? However, your main focus at 700 should be not to hang pieces.

Learn whatever you want, but it is better to learn principles first.