dnd 5e – DND 5e/ High Elf Rogue Arcane caster level 3 heading to 4 – ASI or feat

Hello our campaign is using the phb only. For my turning 4th level arcane trickster I am trying to decide if taking my dex to 20 or choosing a feat is a better idea. Abilities are s/10 d/18 c/14 I/15 w/13 cha/10. Feats I am thinking about are alert, sentinel and magic initiate. Or I could even out my int and wisdom. Any tips are appreciated.