I can't remember what the ideal temperature is, but it depends on how much moisture is in the air, basically you need to control the RH level ( relative humidity ), which is the balance of humidity & heat, so you'd actually need to have some control over heat too ( with windows & radiators ), and it will depend on what country you live in, or north or south etc as moisture & heat levels are different in different areas. Changing the heat level in your room/house will change how much humidity is in the air, like raising the heat level which will reduce the humidity as heat draws out moisture.
When it comes to humidity you don't want to remove all the moisture in the room as this will be very bad as it actually dries out your collectables making them dry and brittle ( this is why old papers like comics start crumbling ), the key to controlling the RH level environment is getting the right balance. Your collectibles actually need some moisture to keep them in great condition, mostly when it comes to papers and card as those materials are manufactured with moisture already in them to keep them firm & supple. The main danger with collectibles is too many rapid or large changes in the RH level over time, too much moisture constantly evaporating and re-entering the materials is what can make ink colours change and cause paper warping etc, so the more these changes are limited the less damage is done ( constantly opening and closing a window in your collectibles room can cause bad rapid & wild swings in RH ). And if you plan on trying to control RH levels then you'll 100% definitely need a dehumidifier and an RH & temp monitor. Apparently though you can actually have a fairly high or low humidity level as long as it's kept fairly stable and not wildly changing up & down.
All this info might be a different story for plastics though, RH levels have different effects on different materials.
The best thing to do is do a google search for controlling 'relative humidity' as there is quite a lot of info on it and can take a little while to learn & understand it as there's a bit of a science behind it, but you can also find out what the optimal RH level % will be for different materials ( a lot of websites will have slightly different opinions on which % ).
The glue??.. oh great you've got me thinking about that now! lol