There are three way you could go about picking a deadline.
1. Decide how long you want to spend on it, and pick your books and areas of study to fit the time available. It's all too easy to look at a genre from outside, or even one you're familiar with, and see so much to learn that it leads to being overwhelmed and choice paralysis. It's also easy to decide to do All The Things, make a reading list and to do pile that will take the rest of your life, and then make yourself miserable failing to do it. Setting yourself a deadline should help with this.
2. Decide on what you want to get done and set a timescale based on it. This is the NaNoWriMo approach - "I will write 50k in 30 days!" If you know you want to write a 70k novel and read X number of books, you can plan around how many words you can write and books you can read to figure out how long it should take.
3. Decide on what you want to do, but leave it open-ended. This is actually not an approach I'd recommend. Time is finite but procrastination is infinite. Picking an end date means that choices have to be made about where this thing is going, rather than just planning it forever and never actually starting. Or finishing.
The important thing is to work with the free time you have - a writer with a full time job and three kids is likely to have less free time than one with no kids and/or no full time job. Some days it's just not possible to write, because of work, family, or general life commitments. That's fine. Goals need to be realistic, and if it's not realistic for you to write every day, then don't. What's important is to make the space for writing every day, so if you can't write do something else - read, listen to a podcast, whatever. Just make it related to your goal.
There are several well-known events in the writing calendar that can fit in with your timeline. The obvious one is NaNoWriMo in November, but there's also Camp NaNoWriMo, a "virtual writer's retreat" that runs in April and July. Also running in April and November is the Poem a Day Challenge where a poetry prompt is posted every day for a month. There's also Story a Day in May, which does the same thing with short story prompts (although to be honest some of them seem more like exercises).
I've been posting these every two weeks, but it's actually Christmas Day two weeks today so I'm going to leave it three weeks until the next one of these.