If you build it they will come
That is the radio signals and contacts will come.For the new ham getting on HF, putting up an antenna can become an obstacle that stands in their way. HF antennas take space and some bands taking lots of space. There are all sorts of opinions of what is best. There are all sorts of technical detail such as insulators, wire type, baluns, feedline, etc. And then there is the problem of where to put it and how to support it.
Often this can cause a sort of paralysis.
So where to start?
A good place to start is to recognize that there is no perfect antenna and that any antenna is better than none. Also recognize that it can be fun to try something and change it for something else. The basic construction materials for antennas (wire, feedline, rope) can always be re-purposed from one under performing antenna experiment into another hopefully better antenna.
Also recognize that for basic HF operation with 100 watts, there isn't a need to go overboard with insulators, baluns, etc. A piece of wood or a PVC plumbing fitting with a couple holes will suffice for a center insulator. A nylon rope will provide enough insulation at the ends.
When looking at where to put the antenna keep in mind that dipoles are very tolerant of bends. When running 100 watts, if you use insulated wire, the wire can be looped over tree branches. There is no need to make it sit out in completely open space between supports and strait runs don't make much difference. You will be amazed at what antennas will tolerate.
Don't worry about getting it in the best position getting it highest. Get something, try it, and improve on it next time. Inverted V antennas are a great alternative to dipoles as they only require one support.
Don't worry about making an antenna work for all bands. Focus on one and like 40m which is a good band for some day operation and some night operation. 20m or 15m for more distance although more daytime oriented. 20m or 15m also can be easier because of their smaller size.
The ARRL Antenna book can be a great source of ideas as well as technical reference.
Commercial antennas, while perhaps not as much fun as building your own, can let you get started and some models are multi-band.
Those magic boxes called antenna tuners can also be helpful, but a word of caution here. While they can match an antenna and make your rig happy, as well as being used in many circumstances without significant degradation, they can also be mis-used. If used the wrong way such as correcting very high mismatch when using coax can result in most of your power ending dissipated in the tuner and feedline rather than radiated. For the beginner it is best to use a tuner with commercial antennas designed to work with a tuner such as the (G5RV) or only use the tuner match to antennas that are mismatched no more than 5:1.
In the end though, you can't work them if you don't put up an antenna. So don't angst over what is best, just put something up to start with, use it, and improve upon it.