All gears can have minion stats. It doesn't matter whether it's STR, DEX, or WIS based since all three classes have viable summoner builds.
For weapons, I would suggest two wands. Staff, I believe, is more for Cinderblades because I noticed that Staff stats usually contains a lot of _% chance to ___ when hitting, which is not needed for Tinkers. Tinkers need as much minion damage as possible and two wands can provide that. Two pistols are also not recommended because I haven't seen pistols with minion stats.
For plus minion count, I think some necklaces can provide that. However, it's mostly through a skill gem which you can craft using the scroll/parchment/blueprint that you get from relic runs, a few other materials, and a very rare magic rune crest. It acts like a jewel that you can place in sockets but it increases the level of the skill instead.