Yes, you can leave your hair wrapped in a towel for an hour or two, or even longer. If you "plop" (or "plunk") your hair, you can also sleep with your hair in a plop. Here
's a YouTube video that shows how to do it.
All gel does not have silicone. Just use a silicone free gel. LA Looks is a cheap, silicone free gel which is widely available in the US, and there are a number of others, such as Garnier Fructis Spray Gel, Aussie Instant Freeze, Herbal Essences Set Me Up Gel Max Hold, Herbal Essences Tousle Me Softly Tousling Spray Gel, Suave 8 Gel, CURLS Creme Brule, and Garnier Fructis Style Fructis Style Pure Clean Styling Gel.
You can use the same conditioner as your leave in as you use for your rinse out. There's no need to purchase one that's labeled as a leave in.
I use a silk pillowcase, and just sweep my hair up toward the head of the bed as I lay down. Silk pillowcases are available online fairly reasonably. I've paid more for cotton pillowcases than I have for the silk pillowcases I use now, which I got from Dharma Trading Company
(NAYY, just an extremely happy customer).