So far there is nothing that matches the sound of a real string orchestra yet. In the meantime, you can get amazingly good sounds while on a limited budget. To carry this feat involves a combination of arranging, programming, recording and mixing skills, but most software sequencers provide all the tools you need to have a stab at it. Quick fixes to transform a rookie string arrangement into something more musically effective.

What to do in the gaps?
Try to direct the strings part into gaps in the arrangement , they can be tricky to pick out in a busy mix,so this could work out well. Gaps such as between lead vocal phrases.

How to make strings that are playing alongside other rhythmic parts more audible?

You can try by getting them to switch notes on beats when no-one else does, even if this is simply shifting to a different note-spacing of the same chord. To achieve more audibility and less mix-clutter, you could park the strings on frequency ranges where nothing’s otherwise happening in the arrangement, also the best arrangements prefer to use variations of instrumentation to help support the structure of the song.

For the inner strings (second violins and violas) try rhythmic figuration to keep the track out of boredom, even if it’s just repeating notes, or swapping notes with each other in some kind of rhythm. When it comes to the outer parts the best thing is to conceive them into melodies in their own right.

Give Low Instruments Enough Space

Leaving bigger gaps between low parts, it’s also not a bad idea to give the low parts the longer notes, leaving fast runs and figurations mostly to the upper strings.

How to get more satisfying sounds?
It is commonly found in busy commercial string arrangements, a harmonized string line that sounds like a single one. Although the harmonies are particularly obscured by other instruments, they definitely help give the top-line melody more body in the mix.
The easiest way to harmonize a melody is to copy all the melody line and
paste it either three, four, eight, or nine half steps below (listening for the one that works best); and then adjust any notes that don’t harmonize well to the nearest neighbouring notes that do. It’s particularly common for keyboard players to treat the ensemble like a keyboard patch. A good arrangement showcases the individuality and independence of the players, even more so than a keyboardist’s fingers.