You get a spear upgrade later in the game as part of the main story. Focus on obtaining ALL the purple bows though over time. They all give you access to different arrow/bomb types. Personally I never used the rope or tripcaster in all my 3x re-plays of the game unless a Hunters quest called for it. I was strictly bombs/arrows/traps mostly all the way through.
Grab the bow that grants you Fire arrows asap (godsend vs glinthawks), and the bow that gives you access to ice/corruption/shock arrows (forgotten the name).
Must confess I didn't think much of the first Cauldron. The other ones were a lot better.
Thanks, will do The bow I have has fire arrows (Carja War Bow). Yeah, I haven't used the tripcaster much so far but it's nice to have for some variety. However, I'll probably be playing like you, so bow/sling/traps mainly.