You could use one array with the relevant info in columns.
Using your items as an example it could look like this :
(add/subtract) / (value) / (buff) / (turns)
+ / 2 / str / 2
- / 1 / int / 2
+ / 1 / str / 10
+ / 1 / str / 3
And you run through it like for each row,
if y2 = str, if y0 = + then strength(variable)+y1, if y0= - then strength(var)-y1
if y2 = int, if y0 = + then int(var)+y1, if y0 = - then int(var)-y1
and so on.
Then after applying the buffs you subtract 1 from y3 for each row.