Hey Thomas, it is against the community guidelines to give suggestions for investing because people much make decisions for themselves and be liable for the consequences. So you won’t get anything like “invest in X and you will be fine”
However, if you do not have ample experience in investing, you may consider ETFs like FTSE 100 or FTSE 250. Should you have invested £100 in the former 10 years ago today, you would have had it valued at circa £170 today with some decent 2 to 3 per cent annual dividend as well. The latter would have been about £300 with some 1 to 2 per cent dividend.
But remember, past performance is not an indication of future and investing in the market will not guarantee reasonable returns within less than years (even after five years they are not guaranteed, just significantly more likely).
The safest decision would be to find a few ETFs you like (even those FTSE 100 and FTSE 250) and keep investing your spare cash in them (on the proviso that you do not need that cash in short run). Reinvesting your dividends will also be a wise decision as it will help to gain the benefit of cumulative growth.
You can read other users’ investment stories and strategies (NOT recommendations) here.