We don't really do drug recommendations here. And "safely" is such a vague term - we don't know anything about you, what's safe for you personally, what your definition of relatively safe would be, what kind of effects you are looking for, or what drugs you have access to. All you can really do is research different drugs and their effects, side effects and risks and make a decision for yourself.
As for the drugs mentioned above: I wouldn't go with recreational-dose DXM if you want to be functional at a festival, I especially wouldn't try it for the first time in that type of setting, and I'd research it a lot beforehand (there is also debate about how safe it is to take in high doses), same with ketamine. As for amphetamines, they can definitely be addictive, although they don't cause a strong physical dependence like opioids or benzos.
(Honestly, I can't even think of any drugs that would fullfil all of the below:
a) safe
b) not MDMA
c) not a psychedelic
d) not an opioid
e) fun at music festivals, has recreational potential, etc
f) doesn't have potential for addiction
g) would allow you to remain cohesive enough not to lose your group or get kicked out, etc (also we can't know how a specific drug is going to affect you).
That's a pretty big list of expectations.)
Anyway, I think this thread will just become a big list of random suggestions of drugs to try and I don't really feel that fits with our guidelines (to answer specific questions about a drug and to help people reduce the harm from drugs they're already planning on using), so I'm going to close it. If there is a specific drug you are thinking of trying and you want more info on it please feel free to post a new thread.
Please PM me if you have any questions.