Pick up some Boveda packs:
I ordered 75% relative humidity ones and I found it made the weed too damp. Waiting on my 58%. The higher RH packs are ok if you don't leave them in the jar too long. I've heard you can find them at head shops around Toronto for a lot cheaper than what Amazon sells them for.
You want the 58s they are the “Terp shields”
Boveda 58% Humidor Packets - 2 Way Humidity Control Packs- Size 4 - 10 Count Resealable Bag - Cigar Humidor Accessories - Bulk Humidity Packs - Relative Humidity Packs - Humidor Packet https://www.amazon.com/dp/B06XB3NP4C/ref=cm_sw_r_cp_api_glt_fabc_HHT74M6A06BV3666J31F?_encoding=UTF8&psc=1
I usually just grab them on amazon like - https://www.amazon.com/Boveda-Percent-2-Way-Humidity-Control/dp/B06XB3NP4C/ref=sr_1_9
58% or 62% are good. someone mentioned 58% for vaping and 62% for smoking. I will do 65% occasionally for pressing. any of those should be fine. the ones i linked (4g) are recommended for a jar with a half oz, they offer bigger or smaller depending on your buying habits.
Those are just air tight bags, you can get those if you want and then throw one of these https://www.amazon.com/dp/B06XB3NP4C/ref=cm_sw_r_cp_awdb_btf_t1_FUgFFbAQ29H1B in the bags
Some people just use these to rehydrate if it gets too dry.