As @westkenshin saind very well, it depends on your skills. You can invest on crits and go like Dex3/Str2/Con1 (until something like 50 Con), for example. That would mean you are rolling for Dex and not Broadhead + Magic Arrow raw damage (Although Magic Arrow CAN crit)
Or you can deal with Str3/Dex2/Con1, Str3/Dex1/Con1 (until 50 con) or even Dex3/Str1/Con1 (until 50 con). It all depends wether you want to secure damage or go for all crits.
In my opinion? Str>Dex is usually more fun to level and more effective along the way. I’d prefer to go Str3/Dex2/Con1 for a good balance between damage and crits for your Magic Arrow, favoring Broadhead instead of Crossfire.