Over the years I have had a search for the perfect but very simple antenna. If you want to work several frequencies a fan dipole is your best bet. A very simple 2 band antenna is a plain 40 meter dipole. This antenna will perform fine on 40 as well as 15 meters. The SWR will be around 2 to 1 on 15 but usable especially if your radio has an internal tuner. I have found for about $100.00 dollars you can buy the new parts to construct a 110 foot dipole, feed it with 300 or 450 ohm parallel feedline. This antenna must have a 1 to 1 or a 4 to 1 balun, from the balen you will need a piece of 50 ohm coax. The shorter the better. Your internal tuner in your radio will most likely tune several bands but probably not all. If you have a good external tuner you will be able to tune all the bands from 80 to 10 meters. Mine has a 1 to 1 balun and I can tune all but 12 meters. These antennas I have described will perform very well and are low in cost. Of'course they won't do the job of a gain antenna like a Yagi. If you want to spend a few more dollars, it is hard to beat a ground mounted vertical. Very simple to make but much work laying the radial system. My 40 meter vertical works fabulous on 40 and very good on 30 meters. You may be able to tune 15 with it also. A full size loop or delta loop is a good close in, say out to 300 to 400 miles. A cloud burner on 80/75 or 40 meters. but it requires lots of wire and copper wire is expensive.
Antennas that are not too good are magnetic loops, end feed 1/4 wave wires, and random wires with a 9 to 1 balun. Also eve trough non-resonant antennas. Trap dipols work but are very narrow banded and hard to make or if you buy the traps they are costly, only use if you can't fit a 1/2 wave one in the space.
If you are restricted on space or have to put your antenna in the attic you have to make do with what you have. I know two hams that have antennas in their attics and do make lots of contacts. My friend (W9BS) in Florida has an attic antenna and I have contacted him on 75, 60, 40, 30,and 6 meters. This is quite an accomplishment for being restricted to an attic space. Even a bad antenna will radiate RF, I have made contacts with a 100 watt light bulb hooked up as a dummy load !
At any rate make do with what you have to work with. I find experimenting is half the fun. A real good feeling is making an antenna that works well.
Good luck in the contest ....... Jack WB9OTX
Dipole calculator HERE
Fan Dipole Information HERE
The image is from hamuniverse.com