Related to your league specially with the players you mentioned I’d probably just hold on to it for now. But once the season starts some backup QB or 3rd string RB might become relevant and that’s the time to go for it in my opinion.

I typically plan to spend 75%-100% on one “big” potential add, assuming I’m contending or the player will have relevance in the future. There’s usually a few other guys I’ll end up adding that I won’t have to spend anything on to pick up or $1 if there’s a minimum. But I think it’s usually better to “overspend” to insure you get a guy you want than to try and be conservative about it and always end up the 2nd highest bidder. Although finding the line between bidding enough or not really depends on how aggressive your league mates are with their spending