In direct response to your three questions:
1). Be very clear about who you are, what you're looking for, and what your assets are in your ad:
Yes: "XX year old guitar player with x years of experience seeking musicians to form a band. My influences are: xxxxxx.... I am still fairly new to guitar, and this is my first time putting together a band. I'm looking for like-minded musicians to get together with, jam & most importantly have fun! I would like to develop mostly original music, but some covers are ok too."
No: "Lords of Thunder" now seeking applications for the position of bass, drums, keyboards, rhythm guitar, and lead vocalist. Must have excellent chops and even better gear. Only the serious need apply, no newbies!! If you are extremely talented, dedicated, and are willing to commit to a world tour, then you could be what we're looking for!
Ok, over-the-top, but you get the idea. Keep it casual for now. If things go well, the music is good and you get along, then you'll probably come together naturally rather than trying to worry about the perfect match & commitment right up front.
2). Yes/No/Maybe so? There's no right/wrong answer here. If you have some stuff that you think is really good, then by all means, start with that. But don't be afraid to just get together, jam, and see what you come up with as a whole. Personally, I think the best bands are the ones where everyone does their thing, and it just fits. That's why the band "works". I don't like creative dictatorships, where someone is constantly saying "play this... no no, play it like THIS..." but that's just me. There are projects and "bands" that have been very successful with one person putting forward most, if not all, of the creative ideas, and the rest of the band just followed their lead. When I played in a band, I wrote songs, but the best drummers I ever had needed no input... they just played really well, and I liked it so I left well enough alone. If you have to offer a lot of input to someone's playing, it may be a sign that you're not really that compatible. I've experienced that a number of times too.
3) Well, you could just put together a band acoustically, but I know that's not you, so some practical advice:
Bare minimum: unless you are going completely electronically (which you can do these days, especially with things like the "Jam Hub), then every member of your band needs to be heard above the drummer. This means you'll need decent amps for bass & guitar, and a PA for the singer if you have one. As a guitar player, watch out for low-powered amps that seem loud in a non-rehearsal situation. You may find yourself cranking up a 20 watt amp to the point where it has too much distortion, and you can't get your sound to where you want it to be and still be heard.
Many drummers love to pound. This can be unfortunate in that it then requires everyone else to be louder. I'd say this is probably the #1 flaw/mistake that new bands make.... the drummers says "ya bro, I like to play HARD!!" and next thing you know everyone is cranked and the lead vocalist is screaming into the mike. Do not let your drummer set the over-all volume... that belongs to the lead singer. The lead vocalist should be able to be heard clearly without needing to strain. This will also allow your band to play with dynamics instead of simply a constant wall-of-noise volume. Imagine that Chris Issak song
Wicked Game ... now imagine if the band played so loud that he had to yell into the mike to be heard... it would change the whole sound. We're not talking style here, just leaving enough "head room" for the vocalist so that singing at less than a scream is an option.
You'll need a place to rehearse too. This can be a curse and a blessing. When you first start, you'll just want to find a place & time where you can just mess around without disturbing anyone. Whatever you can get away with is just fine... maybe there's no PA and the singer just uses an amp.. its ok, you're just trying to get an idea of who does what and how it all sounds. Later, if you get more serious, you may want to look into renting a rehearsal space. Some places will rent you a dry (fingers crossed) warm, place that has power, on a month to month basis. Other places may rent by the hour, and provide a PA for you. Either way, its a good next step to see who is really serious about continuing further when everyone has to start chipping for rehearsal space costs.
The last words of wisdom I'd offer are this: first, don't take any of this too seriously. People start bands all the time, get all worked up, and next you know its over because everyone's egos just got way too big. Be flexible. Let people experiment.
Don't try to make money. As soon as you try to make money from gigs, you start compromising what it is that you're doing. It stops being fun, and becomes a job... unless of course, being in a serious cover band is your goal (but you already said its not). Let the music happen first. If you're good, and you've got something, you'll know, and opportunities will start to open up for you. In the meantime, just have fun with it. You'll likely be in a number of "bands" and play with quite a few different people before finding the right people, so keep it upbeat and enjoy the moment.
Good luck!