what glue to use

You can't really do this hobby without at some point needing glue.
So I thought it would be a good idea to let you know how and what to use.
The 3 main glues we use are PVA glue, superglue and plastic glue also known as poly cement.
In most cases less glue is better than to much as it can squeeze out of the area you are trying to bond and damage detail.

If you paint a figure first then the glue you apply is in fact only as strong as the bond the paint has on the figure (spray paint on plastic has a good bond but not so much on metal). This is not so bad as you might find you wish to are units differently in years to come.

PVA glue is really only used for basing your figures with sand or flock and will give best results if you paint the base first as I find it can fall off if you don't or time.

Superglue is a must have and is a good bet for metal and resin. It is a good idea to pin the figure if it is heavy for added strength and I have found a little green stuff and superglue used together can give a good strong bond. You can also get it quit cheep from some places but this is not always a good idea.
The main problems with superglue are that it is brittle and prone to fail if not pinned though this is not always bad if you want to change your figure at some point. It can also leave a nasty white powdery like effect as it dries and this can damage detail and paint work. It can also if used in to grate amount leave your finger prints all over the figure not to mention stick your fingers together. ( it was developed to stick wounded troops back together after all).
You can get superglue de-bonder but this might not always work. Just be aware that heavy figures you drop on the floor might brake apart on impact and cover a large area.

Plastic glue also known as poly cement only really works on plastic to plastic jobs and works by fusing the two parts together and is a much stronger bond than superglue. This can be good or bad depending on your view point. It is normally a bit less messy than superglue and a lot less likely to glue you to other objects. Just be careful as it can damage your plastic figures beyond repair if you get it all over them

In both cases superglue and plastic glue can have fumes and if the make you feel sleepy or give you a headache stop using them for a while and get on with something else.

Hope this helps and please ask questions if you have any.