Hello PepitaSola, welcome!

When collecting and buying snd selling stamps there is always a value consideration to be kept in mind.
How much you value the value (1?) over the aestetic beauty or pleasure or honour a stamp or envelope (cover) can bring you is an important consideration to remember.
A stamp's or cover's value is based on many things, most of all, usually, the eye appeal, or the condition and the first impression of how it looks or strikes you visually and emotionally.
So, bearing that vagarie in mind, do not destroy something before you know something of what it's value can be, whether to yourself, your grandmother or a potential buyer.
On the other hand, many beginning collectors find that just collecting and sorting and arranging, oh, and valuing, the stamps (and / or covers0 can take up most of their available time, and thus just colelct the stamps themselves.
Knowing enough to judge a cover on value is a learned skill, understanding hand-writing, stamp value, stamp variety vales (colours, perforations (perfs), paper-type perhaps, watermarks in the paper, cancellations and postmark valuation, the actual physical condition of the paper stamp itself (rips, tewars, thins, creases all debalue) depends, I tink, on your own skill at it all and a leaning towards being detail oriented (whether money or art or appreciation of beauty in whatever form).
To simply sort through stamps, get some paper envelopes and sort by country, if worldwide or foreign, first, then by denomination or era. How the stamps seem to fit together, by design, basic colour (older ones only use limited colours), by reigning monarch or president, etc.
Glassine paper is a translucent type of paper that is used for small envelopes to store loose stamps in, search online, if buying there, for glassine. A #4 type of envelope is about 2" x 4".
For older stamps, cancels (cancellations / postmarks) are worth something, whether as noted in postage stamp catalogues or not, as marcophilatelists, like me, collect cancels, and value readable ones and rarer ones.
Note: I will copy some of this to your other thread to help other collectors reading this.