It depends on where you will be using the radio? Are there any trees available?
The best combination of value / performance is a simple dipole.
IMHO, the best multiband antenna for portable ops is a W3DZZ doublet. Sotabeams sells tuned traps for W3DZZ at a reasonable price.
The easiest and lightest portable antenna is an end-fed dipole. It's not as good as a dipole performance-wise but it's very compact and easy to deploy. I've used an end fed made by End-Fedz, model 10/20/40 with good results.
If you decide to go with a wire antenna, get some insulated, stranded, copper clad steel antenna wire from the Wireman. It is hard to break and will never stretch. I've used his 22 (or 26?) gauge wire with great success.
If no trees are available, a compact vertical may be the answer. You can also purchase a fiberglass, 30 ft telescoping pole and hang a dipole or the W3DZZ from it.
I also bought a Buddi-Stick vertical but to be honest it the worst portable antenna I have used. You need to bring an antenna analyzer with you and re-tune the antenna every time you deploy it or change bands. The Buddi-"thing" got a lot of followers that will try to prove you that the antenna works better than a full size Stepp-IR Yagi. LOL. I would not use it for anything below 20 meters because it simply sucks to tune properly. It's a pain ti tune even on 20 meters. I warned you. You decide.