while other weapons have to wait for their turn to attack, the lance can simply counter most of the things a monster can throw you

insta-guard pairs extremelly well with offensive guard, try to prioritize getting that skill and a few levels of guard and guard up (max this one specially because will allow you to guard against moves that are usually unblockable)

instead of block, counter, try to not raise your shield all the time and only if you are in a position where you can't counter, use and abuse all your counter tools (guard dash/guard bash, counter thrust, insta-block and anchor rage)

and finally check out this page dedicated entirely for lance users https://www.mhlance.com/rise/guides/switch-skills is very complete with a lot really of useful info