Your keyword in this case is “lequel” and “qui”.

• “I have things to work with” translates to “J’ai quelque chose avec lequel travailler” or “j’ai quelque chose pour travailler” (“I have something with which to work”)

• “They have no people to talk to” translates to “Ils n’ont personne avec qui parler”. (also means “They have none with whom to talk”.

• “She has none to think about” translates to “Elle n’a personne à qui penser” or “Elle n’a rien à quoi penser” (“She has nothing to think about”)

All of these expressions need and extra word that is unnecessary to use in english, hence your difficulty to deal with those expressions (quoi, qui, lequel etc.)

Most of the time you can use the form:

sujet – verbe conjugué – COD – préposition – pronom relatif – verbe infinitif

For example:

I have nobody to talk with. -> Je n’ai personne avec qui parler.

• "Je" (I) is the subject
• "ai" (have) is the verb
• "personne" (nobody) is the COD
• "avec" (with) is the préposition
• "qui" is a relatif pronoun. It refers to the COD ("qui" when it is a person, "quoi" the rest of the time, except when you put nothing. This point is quite random, if someone have more details I will gladly edit this answer)
• "parler" (to speak) is an infinitive verb
  ("n’" is here because of "personne" which makes the sentence a negation)

With this template you can build sentences like

I have someone to work with. -> J’ai quelqu’un avec qui travailler.

She has nothing to think about. -> Elle n’a rien à quoi penser.

They have problems to deal with. -> Ils ont des problèmes à traiter.