So I'm using proliferate cards in my white/green deck. If I use the ability proliferate on, let's say, Pollenbright Druid, does it allow me to give a +1/+1 to my druid?
The strict answer to the question as asked is usually no. You will not be able to use Pollenbright Druid's proliferate trigger to give +1/+1 counters to Pollenbright Druid herself, because what proliferate does is add more of a counter that players and/or permanents already have - not add new types of counters to those that do not already have those types of counters.
If somehow Pollenbright Druid entered with a +1/+1 counter, say from Chorus of the Conclave or more commonly seen recently (though not for WG like your deck) from Grumgully, the Generous or Rhythm of the Wild, she will already have a +1/+1 counter when she entered and thus that counter can be proliferated by her ability.
Proliferate, as defined by the comprehensive rules:
701.26a To proliferate means to choose any number of permanents and/or players that have a counter, then give each one additional counter of each kind that permanent or player already has.
Pollenbright's other mode, "Put a +1/+1 counter on target creature" can however be used to put a +1/+1 counter on her, but in a deck that uses counters usually proliferate will be the more valuable choice, since it lets you add counters to everything that already has one.
If - with the expression "my druid" - you mean the same Pollenbright Druid, then the answer to your question is:
- No, since proliferate ability allows you to add counters on a given creature only if at least one counter is already present on the given creature.