Best Practices for Managing Leads with Clay and Instantly

Did anyone here find a best practice for managing leads on scale in a setup with Clay + Instantly? Unfortunately, Instantly get's very expensive when upgrading to a larger number of leads so it makes a lot of sense to always keep deleting leads from old campaigns to stay below the <25K leads limit. This is okay when keeping all leads in a Google Sheet but not ideal. The second pain point is synchronisation of LinkedIn leads - currently I use LinkedHelper but there is not really any synchronisation on a per lead level. -> Any cost-effective workarounds how to keep leads engaged and ideally being able to do effective multi-channel campaigns with these tools rather than expensive LGM etc?