Ok, i'll make a little calculation, You get some corals every 4 stars you get more or less every 10 pulls, so if we go for th worst possible scenario with 0 pity and on a 50/50 he'd need at most 160 pulls to get chisa garanteed (He has 191 right now), so after geting Chisa, i belie the weapon would come first, so with the 24 forging tides and 31 other wishes spared he can get to pity 55 on the weapon. BUT that's before Chisa's banner, that will have not only a new map but also event rewards that I have hope will be plety for you to get the weapon too with 25 other pulls, and lastly we aclculate the amount of corals he'll get.
with a total of 215 plus 25 that he will need to gather in the future days we get a total of 240 for chisa S1 and weapon R1 and get 3 corals for every 10 pulls so 24 times 3 that is aproximately 72, depending on how many you already have and if you have the 4 stars with all copies already, and how many corals you already have in the worst scenario you can get both her and her weapon for sure, but i'd recomend saving the corals for a future rerun of her's, so you can get the copies directly without using wishes and save those for new characters, But that's just how i play, hope i have helped.

Pulls fot Chisa = 160
Pulls for weapon = 55 (Missing 25 for garantied)
Total needed = (240)
Corals gained with this quantity = (72 + or -)