how can i get better performance out of my laguna rxe

k&n panel filter. free flow exhaust. nos, fast road cam. fse fuel pressure boost. it depends on your budget but there is plenty you can do.

Do you mean speed or longevity? If it is speed then use a special air flow filter system. It is fitted in place of your normal air filter. Go for a higher grade engine oil.
There are also tyres on the market with racing profiles. Ensure your tyres have the exact pressure specified.
Get rid of any excessive ballast from the car (Passengers etc.) lol.

For longevity, accelerate gently, no wheel spinning, don`t thrash it!

This all depends on how much money u r willing to spend & how much improvement u want to performance wise.
For a small budget l would say to add:
iridium spark plugs
performance chip
performance exhaust
k&n air filter
performance chip
remapped ECU
Performance FMIC (FRONT MOUNT INTERCOOLER)
then u should either add a suspension kit to aid the handling or u could go full out & strip the interior to make it go faster because there is less weight for the car to pull.

If u have a large budget then u could try adding:
Performance Turbo
NOS (nitrous oxide system)
Remap ECU
Boost controller
Up Boost
Performance Exhaust Manifold
Race chip
Upgrade fuel pump
Upgrade Airflow meter
Upgrade cams
Upgrade Pistons
Upgrade Head Gasket
then to cope with all of those mods u r going to need a performance clutch & possibly a gearbox before u old one gives in
many of these parts could be sourced or brought from the renault laguna forums or if u cant find one of those then just try serching for a Renault forum & see if they have any advice for you. Some forums also get discount from big brand performance parts manufacturers & u could save yourself some of ur hard earned cash.
good luck